Davyb,
On the menu at the top of the page you need to click on "File" and then "Preferences".
You then need to click on the third tab "Home Station Data" and then you enter your Latitude and Longitude.
A mistake that a lot of people make at the beginning is to enter the coordinates in the standard format 43° 30' 0'' which is incorrect and will give an error. The coordinates must be in decimals ex: 43.5
The easiest way to find your coordinates is on Google earth. If you have a Smartphone you can also use Google earth that will give the correct format by going to "Options", then "Positions".
Andrew