how do I upgrade my iMac os to the latest

What OS version is currently installed? We cannot answer without details about your iMac. iMacs have been around for almost two decades and there are many different "max" OS version possible.

Start here: https://everymac.com/ultimate-mac-lookup/

Find your serial number and enter it to get the family and sub-model. Without that we cannot proceed.

If that fails, take a picture of the computer and post it here.

This forum covers iMacs made before 2006. Is your that old? If not, that narrows the search and makes find the info you need easier

To use Windows you'll want to look into BOOTCAMP. It is already on your computer under the control panel.

How to install Windows on your Mac with Boot Camp - Apple Support

This guide will get you started.

It appears you have a late 2009 or later iMac. Please do "About this Mac" from your Apple menu (left end of menubar) to get your exact sub-model, the current OS version, and the amount of memory (RAM) installed. Then share that information with us.

Thanks.

AJ

I had a 09 iMac that had troubles updating. I had to delete the file after I downloaded it. It would just get stuck between downloading and actually starting the install. From that picture it looks like that’s what you’re experiencing. But that photo didn’t give quite enough detail for me to see for sure

To update to the latest version goto the App Store and download High Sierra. From the photo you posted earlier it was hard to tell but you were already downloading it or it was already downloaded. I couldn't tell, but click on your launchpad icon and there should be an app like 'install high Sierra' or something to that affect. Click on that icon and please post back your progress.

...control panel...

what is this amateur hour?

I meant system preferences