If you're not sure where to begin, start by searching the primary source portals below. These search across many collections and can lead you to the right primary source database for your topic.
The history vault contains collections of documents that trace key moments in the fight for voting rights. To get to these follow this path: History Vault >> Timeline and select Civil Rights Movement, Civil Rights Legislation, Black Power, etc. Here are some collections that relate to voting rights.
For a case study on how to use History Vault see this tutorial from Proquest.