1st for My main keyword now moving on to others, but how?

For my main keyword I have targeted im currently floating around positions 1-4, now i want to move on and target other keywords. I have tried targeting other similar keywords (less then 20,000 Comp) but not even getting listed into google.
Whats your process of targeting new keywords after you have successfully targetted the main one for blogging?

Are there any good WP add-ons which can help you in this area?

Cheers

Link building for category. You start creating backlinks with the achor of the targeted domain. Exemple. if you target audi exhausts and your blog is about audi cars you make backlinks to youe exhauts category/ page with the achor audi exhaust.

exactly, create another category which is like creating a new page on the domain then target that page like you did your main keyword.