Everyone gave good advice
I would add that sitting them down together for daily training exercises helps a lot. Do very short sessions. Start with 5 minutes and work up from there. With time tey'll associate each other with food or treats. And at the same time, know you're the boss. But make sure you get them to work for their treats. A clicker worked really well for me.
My scottie took a month before accepting casie's existence another month to be anywhere near her and what feels like forever before they actually played together.
Just take it slow. They'll become friends!