Here are some great databases for finding information about medieval studies.You can also check the full list of databases tagged with Medieval studies.
The Internet History Sourcebooks provide copy-permitted historical texts for educational use.
These cover a range of topics but may well be useful depending on your topic.
The very first place to start is with books. You can check out Swansea's holdings or cast your net more widely and order in books using inter library loans service - Click Document Supply Service for more information