How can I collapse the left toolbar into one column instead of a wide column of which I can only see the far right edge (so it is unusable). I am brand new to Illustrator.

Hi Sara, no need to hunt for that tiny arrow if it is off-screen — resetting the workspace will bring the toolbar back into view. Go to Window > Workspace and select Essentials (or Default) to restore the default workspace. Once the toolbar is fully visible again, click the double-arrow at the very top of the toolbar to switch it to a single column. Let us know if the toolbar is back in place after that!

THere is a double arrow in the top (very tiny). Just click on it. CHeck out this how to handle the interface: https://helpx.adobe.com/illustrator/using/customizing-workspace.html