From you profile, select Family tree & tools tab, wikitree tools tab, scroll down and select tests of Cabell's DNA. At the bottom, it should have Add new Test Information. Select appropriate DNA test from the drop down and you should be ok.
Make sure that your gedmatch account has the wiki tree access enabled for all tests, by selecting the pencil icon. It takes at least 24 hours for everything to be connected between the sites.
Hopefully that helps.
