We love it when people help us out.
Search in the Issues as your problem may be a common one. If don't find your problem. Do create an issue. Contributors here will chime in when they can.
Check out the ReadMe. It should have everything you need to get started.
Did a new version of Tika come out and you want to get the Nuget updated? This is very common so check out the ReadMe on Updating Tika. After you've got the new version building, create a pull request. Once it is merged a Nuget will be published.
This project typically has a few up for grabs issues.