It's hard to help without a little more specifics about what you are trying to link.
If you are trying to link family members, spouses/parents/children, you can use the Edit Tab across the top of the profile. For example, you enter a parent, and you have already entered their child, but you didn't link them. Check their WikiTree ID's on the upper right of the profile. So if the father is ID Gilmore-456 and the child is ID Gilmore-123
Click the Edit Tab, on Gilmore-456, scroll down the right hand side and click the (add/edit) button for children. When the next page comes up, enter Gilmore-123 in the WikiTree ID box near the top.
Scroll down and save. You will also have the opportunity at the bottom of the page to check a box for his mother is she is also already entered, before you save.
When looking at a profile in the Edit mode - on the right, you can do this (add/edit) for various family members, Father/Mother/Spouse etc. etc.
Don't know if this is what you are looking for.