The adage is "you can put salt in, but you can't take it out" so taste as you cook.

depends on what the food is. if it's liquid, like soup, yes, you can add to it. if it's a roast chicken, not so easy to fix. Drink lots and lots of water.

You can also try adding a little sugar or honey to balance out the salt.

It depends what you made. If it is something like a sauce or soup try tossing in a peeled potato. It will soak up some of the salt and then you can pitch it out. Julia Child used to suggest it, it works up to a point.

Make another batch without salt and combine the two batches. or if just a little salty, add a bit more of the other ingredients. What did you make?