Why is Communist Activism important?
The success of a movement relies heavily on its revolutionary theory and education, but without the physical practice the movement would not survive. So it is important for every movement, political party, group, etc. to be physically involved in their beliefs. Communist activism is one of the pillars of keeping the movement going.
For every dedicated open communist to practice the theory they learned, they must mingle with the proletariat, they must see their struggles and assist to organize powerful fights for their interests. A communist must rally, they must educate, they must reach out to the masses on a one-to-one level, they must do what is needed to advance the fight for proletarian liberation. That said, a communist must study how to be an activist, they must work on reaching out to their people. The LYCUSA website has a Guide to Activism that goes over important subjects of activist work done by communist activists in the rank and file of the LYCUSA and PCUSA. It is a good guide to study from, but study means nothing without application. So take what you learn from the guide, and apply it based on what you see effective in your area.