Do you want to copy-paste from your local machine to the remote lab desktop?
The basic way
Take a look at the Clipboard button (at the left here):
To copy into the remote desktop, you can paste text to this box, and it will be then available to be pasted in the remote desktop.
To copy out of the remote desktop, you can just copy in it, and the copied text will appear in this box for you to copy into your local machine.
A better way in Chrome!
If you're on a Chrome browser, there's an improvement to this.
At the bottom of the Clipboard menu, click Show More.
Then click Learn How:
A window will open that will explain how to enable clipboard permissions in Chrome:
Follow these instructions, and refresh your browser.