Like I said, I don't think you can bind a key directly to a macro.

So, if you want to use the F1 key to /focus you need to do the following:

1) Create Focus macro with /focus
2) Drag the macro to a slot on one of your hotbars.
3) Bind the F1 key to that slot on your hotbar.

The key is bound to a hotbar slot. I am not sure how BarTender does the bindings but it will be similiar to above.