DoFollow Links don't exist.
Somebody came up with that for some odd reason, but it even leads to broken HTML coding by non-experienced webmaster.
The correct term to use if "Follow link".
And you don't have to do anything to make a link "do follow". It is followed by robots, by default.
<a href="http://example.com">example link that is a FOLLOW link</a>
The coding above is the correct for a Follow link. No REL-attribute (as with NoFollow link) is required, and especially not the attributes "dofollow" as some may imply.
Refer to the link type specification in the HTML spec of the W3C here.
And please DO let us know if you find the "dofollow" specification!