First, you will need to ensure you have a stripe account. Simply go to https://dashboard.stripe.com/register and sign up.
NOTE: If you already have a Stripe account, you cannot use this here unless it was already tailor made for the Marketplace.
Once you verify your e-mail address, you will need to ensure that you populate the necessary business information to activate your account. This is a critical step and needs to be done before it takes real money.