Quick question for the experts. Thanks for taking the time to read this.

I am attaching an arm to a body using polygons. I am using a tutorial and it says to select the body hit enter and select the arm and hit enter and then go to Boolean- Union. Well I do that and I get an error saying

"This command requires at least 2 arguments to be specified ;1 found"

So it doesnt recognize when I hit enter for each one. Any suggestions on how to do it?

If anyone could help that would be great! Thanks.