how do you copy and paste on the imac? my mouse doesn't seem to have left or right click

Click the right side of the mouse.

You can press and hold a control key while clicking the mouse for some functions that were traditionally assigned to a "secondary click" like left or right click, depending on your left- or right-handedness preferences.

Set up your Apple wireless mouse, keyboard, and trackpad explains how to connect them to your Mac.

macOS is designed with multitouch input devices such as the Magic Trackpad in mind. A mouse has limited multitouch capabilities. Using a mouse, you'll be missing out on many of its features.

Use Multi-Touch gestures on your Mac - Apple Support

This is set in System Preferences->Mouse.

There, you can activate or deactivate the right-click.

And as you were told, you can always use control-click as an alternative to right-click.

Apple mice have only one button. There is no left or right.

To generate a right click, hold down the command key on the keyboard and click on the mouse.

If you have a Magic Mouse, you can actually click the right side of the mouse to invoke the right click.

See here: Use Multi-Touch gestures on your Mac - Apple Support

How to identify your Apple wireless mouse, keyboard, or trackpad - Apple Support

Otherwise, if you really need the secondary button, you can plug in a normal USB or BT mouse to the Mac and use that instead of the Apple mouse.