Hi,
I assume you have a OneDrive (formerly known as SkyDrive) account. When you upload your document to OneDrive you can share it with someone. When your file is uploaded goto OneDrive and click the checkbox in front of the file. Then in the top menu choose "Share". You will see a new screen where you can send the link to the other person. In that same screen you will see the option "Receivers can edit". Click that option and click send. The other person will receive a mail with the link in the mail. They can click it and they will be able to edit the document as well.
If you don't have a OneDrive account yet create one first at: onedrive.live.com
Maurice
Hi Lauren S28,
I agree with Maurice, please try his suggestion first. And we also can use Office Online via OneDrive.
More info: Work on Office files with anyone, anywhere, in real timefor free. Create, store, and share documents, spreadsheets, presentations, and notebooks online. Collaboration made easy.
https://products.office.com/en-us/office-online/documents-spreadsheets-presentations-office-online
Hope it's helpful.
Regards,
George ZhaoTechNet Community Support