The first step to configure your eDirectory to integrate with the 2Checkout payment gateway is creating your account on their site:

Follow the steps on the images below.

After having your account set up, the next step is to set up your eDirectory to use 2CheckOut. Go to your sitemgr, ConfigurationsManage Levels & Pricing, open the payment gateways option. 

Now, enable 2Checkout and fill the Account field with your email account used to create the account on 2CheckOut. After that, your eDirectory is integrated with 2CheckOut.