You enter your DNA test information on your own profile. From the drop-down list under "Add" at the top right of your profile, select "DNA Test Information". WikiTree will automatically display that information on appropriate profiles that are related to you. (This will take a day or two, as WikiTree only updates that information once a day.) You should not enter your own test information on the profile of William Cox-23445.
You will also find that it will be easier to make good use of DNA information on WikiTree if you choose a less-restrictive privacy level on your own profile. Right now your privacy level is "Private". I recommend you change that to Private with Public Biography and Family Tree.