Can someone tell me how to add, edit and delete genres in CATraxx?

In the data entry window, simply right-click the Genre field and choose Edit Table from the popup menu:

(To simply add a new genre you can also choose Add, or to edit the selected genre choose Edit.)

You see the 'Edit Lookup Table (Genre)' window. From this window you can add, edit and delete genres:

Another option is to use the Lookup View: Click Lookup: Genre in the view bar (or choose Custom Views / Lookup: Genre from the View menu) to activate the Lookup View with the Genre table selected.