You may be working on different computers when you complete your assignments. There are many ways to save.

Save on your computer

You can save it to your computer hard drive or solid state drive. Most common. You do need to pay attention where on your computer you are saving the file(s).

Save on a flash drive

For portability, you can use a flash/usb drive. The files are on the drive. Keep the flashdrive with you so you can plug it in to any computer regardless of the computer you are using.
You will select the flash drive name (it may vary). Watch the following video.

Using the cloud

If you have access to OneDrive (usually the default cloud program used by Microsoft), when you save your file in Word, Excel, etc., you would select OneDrive rather than the Flash drive.

Emailing a document to yourself.

Let's say that you are in the computer lab and saved the file you were working with on the lab computer. You do not have a flash drive, Onedrive, or Google drive.

Create an email. In the TO: portion you type in your email address.
Attach the document you saved to the computer to your email.
Send the email.

Google Drive or DropBox

If you are planning on using Google drive or Dropbox to save file, you must install the Microsoft Office Plug-in to do so. There are many links for Drive File Stream for Microsoft Office. Google and find the instructions that meets your computer needs. Google drive or Dropbox is not supported.