Usually, this is set up automatically. But if you cannot text, there is very likely something wrong with your text message center. The correct number is +32456002000.
iPhone users can configure the text message center by dialing the code **5005*7672+32456002000# and pressing the call button.
All other users can enter the center in the device settings (usually the settings for your text message app). Our setup guides can help you check this.
Afterwards, restart your device and try to send a text message to yourself. If this does not work, please call us so we can help you.