This is only needed where you have other maps pre-installed (such as Garmin's TopoActive map) or some other third party maps for the same region as the Talkytoaster map.
If you have multiple maps enabled for the same region they will all display at the same time, causing issues.
On most Garmin devices you can enable/disable maps that the Garmin sees as installed via Setup -> Map -> Select Map
On the GPSMap67 series, the maps are hidden in a different menu structure, see below:
Setup -> Map ->Map Manager (ignore Outdoor Map+ and TopoActive Map) and then toggle the maps you want to enable/disable below the other two entries to ignore.
From the Map Page, press Menu -> Map Layers (toggle OFF TopoActive, leave CityNavigator toggled ON).
On the Montana 700 series, the maps are hidden in a different menu structure, see below:
Setup -> Map -> Configure Maps, then toggle Automatic Maps to off, then you can toggle the map (or maps) you want enabled on the active Activity Profile.
Like the GPSMap67, the Montana 700 series has the Map Layers menu too (
toggle OFF TopoActive, leave CityNavigator toggled ON). You can also access the Map Layers menu from the Map display, just click on the layers icon which looks like this: You will then see a scrollable list of maps that are installed on the Garmin's internal storage and the MicroSD card (if installed), you can simply toggle each map from enabled to disabled (or from disabled to enabled) as you need to.