Running Steam Wkshp scenarios in 2015

Okay, I'm completely bamboozled and the TS2015 users' guide doesn't help a bit.
What I'm trying to do should be very simple: running a scenario that I've downloaded from Steam Workshop.
In the first place, just getting a list of (supposedly) downloaded scenarios takes forever -- but that's nothing new. In the second place, once I've selected a scenario, there's no button available to start it, even though what I've chosen is a scenario that ran just fine in TS2014.
I'm hoping that someone who has managed to start a Workshop scenario will be able to tell me how to do so -- no others need comment, especially trolls.
Thanks!
What I'm trying to do should be very simple: running a scenario that I've downloaded from Steam Workshop.
In the first place, just getting a list of (supposedly) downloaded scenarios takes forever -- but that's nothing new. In the second place, once I've selected a scenario, there's no button available to start it, even though what I've chosen is a scenario that ran just fine in TS2014.
I'm hoping that someone who has managed to start a Workshop scenario will be able to tell me how to do so -- no others need comment, especially trolls.
Thanks!