Im trying to free up space on my macAir. I need some help transferring files to an external drive

If you're not creating a backup, you use Finder to copy and paste. You can copy and paste large chunks of data (files and folders) at one time but if you're using a spinning platter hard drive, the process can be quite slow.

Although the output looks like a TimeMachine backup, you can use app Carbon Copy Cloner to make a standard clone that essentially copies your entire data set. You can use Finder with CCC's output to manipulate individual files or folders.

Once satisfied your copies are good, you can delete the copied data ... all of it or only some. Do not delete any system type files or folder; only user type data you created or copied to the Mac.