Most computers have a modem. If yours has one connect this to your telephone line.
Open any file or picture using the relevant software, word, paint, excel etc.
To fax it:-
Click “File” –> “Print”
Where it details the printer name, click the arrow (drop down) and select “Fax”
You will now be asked for the “Fax” phone number and details
Enter these and click “OK” to send the Fax