Each user has a set of credentials which will be needed to configure each SIP-account:
To create a new one, check out thi s quick instruction.
Then install the app version required for your OS and device. You can download it following this link.
Here’s you can choose the app for your PC:
Below you will find the instructions for the apps for your smartphone:
Once you set the configurations, the SIP-account will register successfully. To check the connection, make a test call to your phone number.