For General Legal Research
Most legal research assignments can be done in one of the two major research platforms - Lexis and Westlaw. While their coverage of recent primary and secondary authority is comprehensive, you will find spottier coverage of older materials and you will need to consult other resources to find them. HeinOnline is a good source for historical primary law and documents. You must have an account to access these services.
If you are on-campus, you can search a version of Westlaw. While it does not provide the same rich content, it does provide a comprehensive collection of primary law (i.e., cases, statutes, regulations) and some legal commentary.