The most common issue regarding Styles we get in support is the following:
"I have set my icon on a waypoint, but its not showing on the map."
The usual reason is Styles.
The best way to explain this, is a quick walk-through:
In Settings, if you set GPX Editor to show columns of Line Style, Waypoint Style and Symbol:
If I now plot a waypoint on the map, you can see the Style applied to it, either in GE, or by right clicking, to Styles->Waypoint Style and seeing which Style has a tick mark next to it.
If I then pop into the Waypoint Style Manager, I can see the tick box 'Show Waypoint Icon' is ticked. If this is not ticked, the icon will not show on the map.