Im sorry  - I asked this question a couple times here, and after the second time I tried to figure it out myself. Its seems pretty easy to do. The answer is actually included in the 'take a tour' guidance found when creating an invoice. Its pretty clearly included in the 'add a service' section. Please take a look through it if you could. If I'm right, you guys should be aware of it. If I'm wrong or missing something, which is certainly possible, please let me know.

thx!