If you you want to load up workbench you need to have the Workbech disks. It should be labelled Workbench 2.05, if you insert this it loads up the Workbench desktop. This is the same procedure for games aswell just insert the disk. It sounds like it doesn't have a Harddrive in it so you'll be running all your software from floppies I'm afraid. Anyway hope you have fun!
BTW, how much did it cost you?