site search widget

how do i make a widget that searches site topics and sub topics

In the Admin Panel, Go to Modules>> Forum widgets management>> Find the Search Block and drag it to where you want and hit Save.

Before doing that make sure to display your forum widgets.

to be more exact i want a search widget, but it only searches within topic titles

You can search topics and posts with that default search widget. Plus it also has Advance search which makes it even better.