i'm trying to consolidate my contacts but i dont have the "link contacts" option from the edit contact screen? what do i do?

i've watched a youtube video that walks me through step by step but when i try to employ what i see on the video i realize that i dont even have the "link contact" option after scrolling down in the edit screen for a given contact. i have "add new address" and "add field". any advice would be appreciated.