Setup step 1:
Install and configure the View map add-on located here:

https://www.xf2addons.com/resources/view-map.24/

Setup step 2:
Update the Options page with your Google javascript API key.

Setup step 3:
Using the 'Show map admin' link in the visitors tab, create a map category.

Example:
Description - dealers
Detail - Dealers and shops
Coordinates - 37.339386,-121.894956
Zoom - 6

Setup step 4:
Create a forum where you will have threads of a certain type. For example you would have a Dealers forum. Each thread will represent a dealer which has information about that particular dealer. In the first post of each thread you will need to insert a map bbcode. This code looks like this:

[map=37.339386,-121.894956]View map[/map]
You can get this map bbcode using the View map add-on.

Show the map from the URL:

Add 'showmap' to your forum URL. Note a query string is required, this will be one of your category IDs.
Example:
https://www.domain.com/showmap/?id=dealers
You can create a Public navigation or Widget for the URL which calls a specific map.

Creating a public navigation link:
To create a public navigation link enter these values:
Navigation ID = showmap
Title = Show map
Parent navigation entry = Forums
Display order = 1000
Type = Basic
Link = {{ link('showmap/?id=dealers') }}