All categories and most subcategories should have tools posted in their header. To begin with that will be the links in the related card in the ‘Build’ section.
To add links into the header you can either click the ‘edit category’ icon, or you can edit the 1st thread created in that category (which will normally still be called ‘about’ or ‘general discussion’).
The header will only show up until the end of the 1st line of text, so the format will need to be:
Tools: [link] - [link] - [link]
There is often a delay before it updates. I found it easiest to leave the tab open and move on to the next one, then return to the later and refresh the page whilst clearing your cache. (cntrl+r or cntrl+f5 on windows)