Now I want to mention that contributing your community can be big or small. We all do not need to volunteer for Doctors without Borders or the Peace Corps (but if you do that is totally awesome) to make a difference.
In order to do this reading, you are going to want to separate your major arcana cards from your minor arcana cards.
The way I look at the suits when it comes to this subject as follows:
Major Arcana- Interpret each card as you usually would and use your intuition to help you figure out what that might mean to you as it relates to the community.
Wands-Action (attending meetings, becomes part of community action committees, etc.,)
Cups-Helping on a small scale (Helping neighbors, friends, caring for others)
Pentacles-Using your creativity and/or skills to further issues you care about
Swords-Writing and speaking
Position 1: I would pick between 1-3 issues to get involved with, that way you don't get to overwhelmed. I would recommend you do a different reading for each issue.
Position 2,3,4- Create a full storyline using the cards. The best thing about the tarot is that it spans the spectrum of life, hitting all the important aspects so you can't really go wrong asking a question like this.
The whole reason this spread is so short is because volunteering and getting involved in your community should be simple and accessible.
We all do not need to volunteer for Doctors without Borders or the Peace Corps (but if you do that is totally awesome) to make a difference. So go get to it and let's all work together to make things better.