Connecting 2 opencart sites

Hi I have 2 opencart websites which are a bit similar and i want to connect both of them.

Something like and external link in the header section

Not entirely sure what you mean but you could add a link into the header template file located in:

opencart\catalog\view\theme\default\template\common\header.php

Thanks WhiteBirch

sorry I am a beginner, can you please provide more details as to how I should add the link
and if I need to make changes in any other file
Regards
Mohit