1. Login to the system administration.

2. Navigate to Settings: Providers.

3. Click on "Add Custom Provider".

4. From the "Type" dropdown menu, select "VOIP" or "PSTN".

5. If you have already selected "VOIP", from the "Protocol" dropdown menu select "SIP" or "IAX". If you have already selected "PSTN", from the "Protocol" dropdown menu select "CAPI" or "ZAPTEL".

6. Enter your provider name into the "Name" field.

7. Select other options to correctly configure the provider settings.

8. Click on "Save".