How to put rel attribute as ******** in Links on Indiehackers?

There are many guys putting dofolloww links on Indiehackers ( DA-50).

Wanted to know whats the syntax for putting dofolloww rel attribute in the posts and articles in Indiehackers?

One more question!

Would the post get naturally indexed or will I need to use any indexing service for the same.

Thanks in advance.