Elementary, like Debian and some other Debian derivatives, doesn’t support PPAs out of the box. In order to use them, you’ll have to install `software-properties-common`.
Open your terminal with CTRL + ALT + T and simply enter the following:[code]]czo0MzpcInN1ZG8gYXB0IGluc3RhbGwgc29mdHdhcmUtcHJvcGVydGllcy1jb21tb25cIjt7WyYqJl19[[/code]
Once you’ve done that, you can add PPAs in the normal way. For example, this is a LibreOffice PPA:[code]]czo0MzpcInN1ZG8gYWRkLWFwdC1yZXBvc2l0b3J5IHBwYTpsaWJyZW9mZmljZS9wcGFcIjt7WyYqJl19[[/code]