The ClickSend SMS add-on needs to be installed and activated to see the features mentioned in this this documentation.
How To Use the Ninja Forms ClickSend SMS Add-on:
The ClickSend add-on for Ninja Forms enables integration with ClickSend for sending text messages using SMS (Short Message Service). This has all sorts of uses, like texting notifications on submission or thank you notes.
Connect Your ClickSend Account
1. Login to ClickSend and select API Credentials from the account dashboard
2. Copy the API key
3. Paste the API key into Ninja Forms > Settings > ClickSend API Key, enter your ClickSend username
Setup the Form to Send a Message
To add the action to any form, from the Emails & Actions tab click Add New Action and then the ClickSend action from inside the Actions Window that opens.
Click the new action to open its settings, and map the field you’re asking the user to enter their phone number into to the To setting of the action. To map the field, click the merge tag icon to the Right of the To field and select your phone number field from the list. 