For the time being, responder keywords can only be created through the UI on an approval basis. A responder keyword allows for one text message to be delivered to a mobile subscriber regardless of opt-in status. They are generally used for couponing or information. You can create them as follows:
Login to the user interface with the link given to you at sign-up.
Select the store you wish to create the responder keyword for.
After the store loads select SALES in the upper left hand corner.
Now select NEW.
Enter the responder keyword you wish to acquire and scroll down and click SAVE at the bottom. The UI will notify you if the keyword is in use.
CRM Text will notify the admin of keyword approval. Once approved click SALES.
Now click EDIT and type up your content. You can respond differently to mobile subscriber's who are not opted-in versus those who are opted-in.
Scroll down and click SAVE at the bottom and you may now test your keyword by sending it to 444999.