I have these chain tensioners:
How do I install them correctly on my single speed bike? Do they go on the inside or outside of the frame?
My dropouts look something like this:
Apologies if the answer is really obvious. Appreciate the help.
They look like you want those "in" the horizontal dropout. The bracket should cover the frame and as you tighten the bolt it will pull the axle further away from the cranks, tightening the chain along with it.
Be careful to not over tighten as you want a little 'slack' in the chain. Also, it is very easy to tighten one side more than the other resulting in your wheel not rolling straight (just slightly off center is what I see most often).