How to combine two sheets into one

Hey y'all. I'm sure this has a very easy answer but I'm going crazy trying to figure this out. I have two datasets with all the same columns, and I am simply trying to add one dataset underneath the other on the same sheet. But when I try to just copy and paste I'm getting all sorts of errors. Like saying that the the selected area needs to be the same size as the copy area, or when I try to insert one dataset above the other it overwrites the original. Has anyone had this issue before? Thank you!