Monotote supports a number of external affiliate programs. You can easily connect these affiliate programs to your Monotote account via https://dashboard.monotote.com/affiliates.
Once an affiliate program is successfully connected, a set of webshops will become available for that affiliate program. Depending on the affiliate program you'll need to set some additional affiliate keys per available webshop.
When that's done, the connected webshops will automatically appear in your product browser and you can start using their products on shoppables.