Stripe is available for merchants from US, Canada, UK and Ireland. It is also available for some other European countries and Australia in beta mode (with limited functionality, but still fully operational to receive money from customers). US businesses can accept Visa, MasterCard, American Express, JCB, Discover, and Diners Club. Canadian, European and Australian businesses can accept Visa, MasterCard, and American Express.
Before using Stripe as a processor on your Getsocio site, you should apply for a merchant account with Stripe. You can register your account from this page. After you submit this form with e-mail address and password, you will be redirected to Stripe account dashboard. By default your account is in the test mode, so you would need to activate it to accept money from your customers. For this you should toggle "live/test" at the top left of this page and on the next screen you should fill in the form with personal and business information. It will take certain amount of time for Stripe to process your application and activate your account. Once you are approved for accepting money, you should set up Stripe on your Getsocio site.