Before you can start using paypal adaptive payments you need to get an application id (APP ID). For this you need to submit your application at https://www.x.com/
You can use the login button at the top right and login with your paypal account. After successful login click on "Submit New Application" and fill the online form. Your application will need to be approved by paypal and as soon it has been approved you will receive your personal APP ID.
In IXXO Cart Multi-Vendor Payment Gateway settings activate paypal adaptive. Fill the required information including the APP ID. Click to save.
Now your vendors all they have to do is to login to their vendor account click on payment gateway settings and enable paypal adaptive. All they have to type is their paypal email address, select their currency and click to save.
Paypal adaptive will handle chained payments in one order. Vendors will receive the amount (minus super admin commission) for their sales and super admin will receive the total of commissions.
For testing purposes you can use the TEST ID APP-80W284485P519543T provided by paypal.