Hello @Tamara-and-Viggo0,
Airbnb doesn't provide a specific way to do that.
What I've seen other hosts here recommend and do is to
Mark the listing as pet friendly
Promenently mention a pet charge in their listing descrption
Mention it in messages if the guest asks about accommodating pets
When the booking is confirmed go to "Host", "Your reservations", click on "Send or request money" and ask for the agreed amount.
The guest must then accept the charge before they are allowed to bring the pet.
I'm not sure if you have hosted guests with pets before. I've seen the suggestions below from hosts who have.
Make sure to beef up your house rules saying.
Pets allowed / not allowed indoors.
Pets must be house trained and socialised.
Pets can be / cannot be left unattended in the listing.
Pets must always be under control of the guest.
Whether you accept pets being left unattended if they are caged.
Etc.
Be aware of your country's laws on support animals.
Steve.