I agree with those below, if you’re wanting to do a pamphlet on how to get involved, it should be from your party, telling them the importance of activism, of being in a party, and what organizing can achieve. That has to be tailored to the needs of your community and people’s local material concerns.

As far as a short marxist essay for beginners, IMO there’s no better than Lenin - The three sources and three component parts of marxism, and Engels - Principles of communism.