Go to your email login page (https://outlook.office365.com) and sign in with your email and password. Click the ‘Log In’ button.
When you are logged into your email in the Mail section, click the button that looks like a gear top right and select ‘Office 365 settings‘ from the dropdown.
You will now be an an Admin page. Select the ‘Software‘ option halfway down the screen.
You should default into the ‘Office‘ tab, which will show the entire office suite available for download and which devices it is currently on. Click ‘Install.’
If you need to download the OneDrive app by itself, all you need to do is select the ‘OneDrive‘ option under ‘Software‘ on the left and then click ‘Install.’
2007 & 2010 Patches (optional):
If you’re running Outlook 2007 or 2010, there is a compatibility patch that you need. Find this under ‘Desktop Setup‘ under ‘Software‘ on the left and click ‘Install.’