Davinote has a Promotions tab, but the deals you can act on today live on each business's own profile, as services with a reduced price. This is how to find them and how they behave.
Look at a business's services
Open any business and go to its Services tab. A service on offer shows its reduced price and the discount next to the normal one.
Check the Promotions tab
The fourth tab gathers offers across businesses. If it is empty it says so plainly rather than spinning — that means there is nothing running for you right now.
Pull down to refresh it
Dragging the tab down from the top asks for the current offers again.
Book the discounted service
Add it to your cart as usual. The reduced price follows you to the checkout — the price on the service card and the price you pay are the same number.
Watch the day you pick
Some offers only run on certain days or between certain dates. Choosing a day the offer does not cover puts the service back to its normal price and the discount line reads zero.
That is the offer expiring for that day, not an error. Pick a day inside the offer to get the discount back.