When you first bring the cat home keep it in one room for at least a week and possibly more depending upon it’s personality. Some are very skittish while others are more bold. But give the cat time to get adjusted to you and the house before introducing it to the dog.
They will sniff each other under the door probably. You could also take some washcloths and rub one on each animal and then on each other.
The first time they meet the dog should be on a leash so you have some control. Keep the cat in its’ carrier till you see how they act. Praise the dog a lot and even give him a treat so he associates kitty with pleasant experiences.
When they seem to have settled down a bit with each other put up a baby gate in the cats room. This way you can safely leave the door open and give the cat a refuge if things arent going so smoothly.
You probably should not leave them alone with access to each other until you have had a chance to observe them when you are home with the baby gate up to see how they do. As long as the gate is up the cat can jump over it if she wants to get away from the dog and is free to interact with the dog on her terms and when she feels safe.
Don’t rush the whole process and have lots of patience with both of them and itshould likely work out ok.
During the whole adjustment period be sure to give the dog lots of positive attention and even more so than usual so he doesn’t feel jealous.
Slow and steady are the key words. You want to be like the tortoise not the hare.