Add rel = "dofollow" to internal links
What some people call a "dofollow" link is just a normal link - i.e. a link that is not tagget with the rel="nofollow" attribute.

In other words, this what a dofollow internal link looks like:

&lt;a href="target.html"&gt;target&lt;/a&gt;


There is no dofollow (or similar) attribute you can add to the link.  The absence of nofollow is what you're looking for.