So in the timeline when I click the plus sign to add a track, everything is greyed out. I can't add audio, video, or subtitle track. Why is it greyed out and how can I add tracks?

I suspect you're looking at the timeline for a menu. Menus have only one video track, one audio track, and no subtitles. If you're trying to add something to a video, navigate into that video first by double-clicking it on the Project Overview window or right-clicking and choosing Navigate Into.

If you already see the video you want in the Workspace, then you may have mistakenly added your video as a menu background. Start over and this time drag the video to the Workspace instead of to the timeline (which is how the above mistake usually happens).

Hope this helps,
Rob