As soon as you have credit, the SMS channel will be activated for your account and you can begin to send campaigns.
Your available credit is always displayed in the 'Current Status' section, located in the upper right corner of the Campaign Management Panel. RMC checks the cost of each campaign before launch to make sure that you have enough credit to cover it. If you have insufficient credit at any time, the campaign you are about to launch is put on hold and you are notified so that you can top up your balance.