That's removed in the 076b version. Use their inventory to dress them and make them your followers by clicking on the small, red icon next to their interaction button. You can add both slaves to your party this way - much faster.
It's a bit confusing - I'm redoing the merc system right now (didn't have time to add that to the 076 version) so they're left in the old system and the girls are in another.
The 0.7.7 update in a week or two will completely redo how you hire mercenaries. You can now search for them in taverns, warrior halls or on the map, and more freely choose how to build your crew.