Marqqs
2
Hallo Phil,
welcome! 
As far as I remember, I had to import the data from my Garmin device directly via QLandkarteGT or MapSource POIs to get the POIs into a GPX file. The files on the device’s MicroSD card don’t contain the POIs.
If you upload a GPX file which contains POIs, these POIs are stored in Openstreetmap database. To get them visible in Potlatch, you have to start this Editor via your OSM account:
GPS Traces → See just your traces
Now Choose your trace. Then click on “Edit this trace”.
I prefer this alternative: http://wiki.openstreetmap.org/wiki/DE:Upload_Waypoints#Arbeiten_mit_der_Software (German).
But both ways will work.
Markus