First, get your MapBox key as explained in the following article: KB439962: How To Activate MicroStrategy Geospatial Services
Then follow the steps below:
Note: If you have already configured ESRI or Google Maps, directly deploying the Mapbox plugin may inhibit you from using ESRI or Google Maps. To use all configured map types, you must merge all keys in one map.Config.xml file and delete the rest.
For example:
<mc><ec><apps><key><!--<![CDATA[ESRIKey]]>--></key></apps></ec><gc> <mk isPremier="false"><!--googlekey--></mk></gc><mbc> <tk><!-- mapboxkey--></tk></mbc></mc>