Ok well the buttercream recipe i use calls for shortening salted and unsalted butter,vanilla and milk.i forgot that i didnt have any salted butter so i went ahead and just used unsalted,well now i think its to sugary what can i do?

Add some pickling salt.

My recipe calls for a teaspoon of salt. That will cut some of the sweet taste. I am not an expert but it works for me.

I'd add a pinch of popcorn salt. That's what I used to use in my old "decorators" buttercream recipe. It's superfine and will disperse through nicely without having to add too much.

I always just use a little salt.

If you don't have popcorn salt as recommended above (and I would only use about a 1/2 teaspoon) you can grind it down to a finer consistency than regular table salt. Regular table salt will not have time to dissolve if you add it to the batch after it has already been mixed and will leave pockets of the bc saltier than others.

BTW popcorn salt = pickling salt. BUT the popcorns salt is more expensive.