Hey there, Donna Murray
I can see the Independent Adviser answered part of your question. However, I just wanted to post to answer your other questions I have quoted underneath from your main question.
I need to know if one Drive automatically uploads after purchase
This depends on how you have set up OneDrive on your computer/device. If you have it set up that it will automatically back up important files, then it will. If you haven't enabled this option, then it won't.
You can check by clicking onto your OneDrive icon on your notification area

You will then need to click onto the gear icon on the top-right.

Then click onto 'Settings'

You will have a dialog box open for the OneDrive settings. You will want to click onto 'Manage backup'

This will show you what folders are backed up and are syncing directly with OneDrive.

You will want to have a look at the toggles on the right-hand side of each folder.

If the toggle is to the right-hand side (like mine are), this shows they are backed up and are syncing. If they are on the left-hand side, then the folders are not syncing to OneDrive.
or will I receive instructions to install etc.
If you have Windows 10 or Windows 11 as your operating system. OneDrive is apart of the operating system. This means you will not need to install it onto your computer.
You can start OneDrive by searching 'OneDrive' in the search bar. To do this, please click onto the search bar on Windows

Then search OneDrive. You will then see OneDrive appear in the search results

You will want to click open

This should start OneDrive, if it wasn't started before. It will then prompt you to sign in and set it up on your computer.
Previous versions of Windows, such as Windows 7 or Windows Vista, you will need to install the OneDrive sync client onto your computer. However, I am unsure if Microsoft still has the download for those operating systems as they are no longer supported.
Also will I be alerted prior to renewal time?For monthly subscriptions, there is no notification for the money for the subscription being deducted from the account.
If it is a yearly subscription, you generally get an email reminder telling you that the subscription is due, providing a due date, and how much it will cost. This is what happens with me and my Microsoft Family subscription. I get an email telling me that renewal is approaching. It tells me how much it is going to cost and when it is going to take the money out of my account.
Hope this helps,
Nathan