Alright, first you need to subscribe to your map, then you need to go to
\Documents\My Games\Company of Heroes 2\mods\scenarios\subscriptions
There you will find all the maps youre subscribed. then you will need
this
Then you just need to open the map (Looks something like this 202808883.sga ) with the sga extractor you downloaded, that will create a folder in the subscribed maps location. And then you will just open the folder and find the sgb file and open it with the world builder.
And also if you want to update the map, you need to save the map to:
Steam\SteamApps\common\Company of Heroes 2\CoH2\Data\Scenarios\MP
Then you just need to hit the update button on the published map
And if you don't want two versions of your map in the map list in coh 2 i suggest to unsubscribe from your map