If you are an agent you would have your client complete a rental application. This is a car form. You would specifiy the amount you are requesting the lease be in the top of the form (if it's an offer I'm assuming you are offering less than the asking price). The terms of the lease would be negotiated once the tenant has be accepted via the lease application.
You may also want to negotiate this in advance in person with the other agent or via phone or email just to make sure you aren't wasting anyone's time.
The Reavis Group
Keller Williams Wilshire
Hope this helps. If not, please feel free to clarify with additional details.