To create a Web Store navigate to Store Operations > System > Manage Stores as shown bellow.

Click on "New Store" button and you will get a screen as shown below. From here for "Store Type *" choose "Web Store /Product Channel" and fill in other fields: for example for

Store Number - you can use the next free number
Name - you can use "Main Web Site"
Short Name - you can use "WEB1"

As soon as all fields are put down click on "Continue" button.

After clicking "Continue" button you will get a page like this.

The following drop downs should be automatically filled in:

Mage Instance *
Mage Website *
Mage Store *


If these drop downs are empty and there is no suggestion to choose, follow these steps.

Navigate to Store Operation > Linked Apps > Magento Instance > Magento API Settings > click to edit the API and click "Save" button.

After go on filling the requested fields. For example for: 

Register Unique ID WEB_1
Register Name Web Sales
Store Email (Admin Email) - your admin email

After all these are done click "Save" Button