Select the text, file, or item you want to copy
Press Command + C to copy
Click where you want to paste
Press Command + V to paste
To cut instead of copy, press Command + X
To copy and paste using the menu, select Edit > Copy and Edit > Paste
To copy and paste with a trackpad, use two-finger click for the shortcut menu if needed
To copy and paste between apps, repeat the same copy and paste steps
To copy and paste files in Finder, select the file, press Command + C, then press Command + V in the destination folder