The first thing you must do is create a squad. As a starting Level 1 trainer, you can choose up to a maximum of 12 Pokémon, including gender. You must also indicate the Level of the Pokémon at all times. For example:
Male Pikachu (Level 1)
Female Butterfree (Level 1)
Genderless Voltorb (Level 1)
You may even give your Pokémon a name, like Ishizu: Female Skitty (Level 1). You can check the Pokémon Level Acquisitions section to check to see which Pokemon you are allowed to have on your squad for your current trainer Level.
Level 2 Pokémon in Initial Squads
Since a Level 1 Trainer starts with a maximum of 12 Pokémon, a Trainer can reserve only 2 Pokémon of those 12 from the Level 2 acquisition list, except for the non-evolvable Pokémon. The non-evolvable Pokémon are displayed with a blue, green, or red color on the Table. When a trainer goes up to the next level, so does the Level 2 Pokémon (to LV 3, 4, and so on).
Now if both your "initial" Level 2 Pokémon are on a trainer's squad at the same time during a battle and one of them is used, there is a chance that the Pokémon may become unruly and may not listen to its trainer. So beware of this, trainers.
Signature Moves
For each Pokémon, you can choose to append a signature move to that Pokémon. If you don't want to make a signature move, you can say "No Signature Move" below the Pokémon's name. Read the Signature Moves section for additional information regarding Pokémon signatures. All submissions are to be posted in the Squad Submissions thread to be approved and/or disallowed by a League Official. Make sure you post your Pokémon name and signature move on separate lines in your squad post.
Levelling Up
For every Level you go up, you can add up to 3 Pokémon to your squad. You may also win additional slots through tournament promotions. If you don't remember your maximum number of Pokémon, you can always double check the League Table on the website. Gym Leaders and Trainers automatically get an additional 3 slots for their Gym Pokémon in addition to the level bonuses that they've already accumulated.
Each of the 3 additional Pokémon that you add to your squad must be
(1) A Level 1 evolvable Pokémon from the acquisiton table or
(2) A non-evolvable Pokémon from the acquisition table that satisfies your Trainer Level. In this case that Pokémon must start at Level 1
If you wish for the new Pokémon to "catch up" to your current Trainer Level X, it has to be on your squad in X-1 matches (for example, 2 matches to reach Level 3). Each match that Pokémon finishes, it then increases it level by 1.
Also when you reach the next Trainer Level, and a Pokémon in your squad evolves at that level, just post in the Squad Submissions thread saying you want to evolve your Pokémon and display the evolutions just like posting an addition to your current squad. An example of the format is the following:
I'm evolving these Pokemon in my Squad:
Ishizu: Female Skitty -> Female Delcatty (Level 3)
Same Sig
And it will be approved by a League Official. Remember, for a Pokémon that needs happiness, trading, or a stone to evolve to the next level, they don't need the particular item. It takes 2 Trainer Levels further than the level of its previous state for the evolution to happen. For example, you can obtain a Growlithe at Trainer Level 1. You can evolve that Growlithe to an Arcanine at Trainer Level 3 without a Fire Stone.
Shedinja
This is how the PASBL will handle the situation of Shedinja, the Wonder Guard Pokémon.
If you have an open slot on your squad when you Nincada evolves to Level 2, then you will obtain a Shedinja and a Ninjask; otherwise, you can only earn a Ninjask. In regards to ability, Shedinja can only die to super effective attacks, but is guaranteed to die from 1 hit. Otherwise, Shedinja cannot be KO'ed. Also because of its ability, you may only have no more than 1 Shedinja on your team.
To figure out the chance for KO, a percentage was created based on the Level of the Opposing Pokémon and Level of the Shedinja. This percentage is as follows:
(Opp Pokémon LV)/(Shedinja LV) * 50%
This percentage value cannot exceed 100%. The percentage represents the chance that the Pokémon gets KO'ed from a super effective hit, not the chance of the attack actually hitting. Rock, Fire, Flying, Ghost, and Dark attacks are effective to Shedinja.
Also in the anime, Shedinja isn't transparent in its Bug/Ghost type form, so it can be hit by all physical attacks.