Most PVP fleets are composed of ships that all follow the same idea, and have the same or similar fitted modules. We call these kind of ship fittings ‘doctrine fittings’.
A doctrine consists of :
A Fleet Commander (FC) creates these ships fittings with a full fleet in mind. So each ship in the doctrine complements each other.
The fittings are stored and maintained on the APOC alliance and Phoenix coalition websites.
When you log into the site, you can find them on these pages:
Most doctrine ships are sold on contract from the coalition PVP staging location.
Be sure to have the following settings selected on your contract search window:

If they are none available on contract, you can also check the market hub in the PVP staging. As a last resort, you can also ask around on the alliance and/or coalition Discord server in one of the market channels.