XASTIR is a great package which provides a graphical user interface (GUI) to APRS data, and although it’s a bit slow on a Pi it does work. Installing it from a debian package is relatively straightforward
Once you have xastir installed and X running, you will find xastir listed under ‘other’ – alternatively open up a terminal window and start the program by typing xastir – this throws up warning etc. in the terminal window which can be ignored.
It will take a bit of time to start – the Pi isn’t the quickest processor on the block, but when it settles performance is tolerable.
You will be prompted for your callsign and location etc. – this is fairly self explanatory but the xastir website will be able to help. One thing I will say is that the first thing you’re likely to want is a better map – go Map > Map Chooser, select the four Online/OSM_cloudmade_3.geo maps for Open Streetmap, and deselct the default worldhi.map. It will take a bit of time for the maps to be downloaded but they’re very good.