Hello @Douglas115,
They need to send a reservation inquiry for you to be given the option of sending them a special offer.
They do this by going to your listing page and clicking on the "Contact host" link. It's just below the description and above the "Amenities" section. They'll be asked to enter dates and they can also type a message. You will then see the option ot pre-approve, decline or send a special offer.
On the Android app the "contact host" section is near the end of the page, just above the "Similar homes" section.
The post below has iinformation on the difference between a reservation inquiry and a reservation request.
Difference between a Reservation “Inquiry” or “Req... - Airbnb Community
Steve.