First of all write down a brief introduction about your organization, or yourself if you are acting in individual capacity, and remember to include your past experiences in it. If you have developed a project similar to the one you wish to propose, give it a separate paragraph and write in the details about it.
Now come to the problem on hand, tell your audience about the nature of the problem and how you plan to handle it. Explain how it can be categorized under the community involvement tab, and what you intend to do with the money.
Explain the problem at hand and write down how involving the community will will solve the problem. For example, if there is a problem of garbage or littering in the area, you can organize the youth of the neighbourhood to clean up the area. If you require any assistance from a government body, mention it in the document.
Explain the project in such a way such that the organization which you are approaching decides to fund your project. Always write in easy to understand, simple English.
Follow the KISS method, which specifies that you should keep it short and simple. Try to go for a one page document.
Attach supporting documents to verify your claims about the past work.
If you have an alternate proposal for the same job, attach it with the package.
It will be very beneficial if you can attach a sheet having the signatures of all the community members.