This article describes how to upload files on Microsoft Teams.
There are a couple ways to upload files to Teams. Once you upload a file, you can also share a link to it. That way, you don't have to upload multiple copies of the same file to share it in different places.
Note: Files uploaded to team/channel will remain within that team regardless of the uploader's membership status. For more details on the file ownership, please visit the file ownership in a team vs. a chat page.
Step 1. In MS Teams, go to the channel you would like to upload this file.
Step 2. Start a chat conversation, and select the "file upload" icon.
Step 3. Upload your file by either selecting "Browse Teams and Channels", "OneDrive", or "Upload from my computer".
Step 4. When you're ready, select "Send" icon at the bottom right corner.
Step 1. Go to the channel you would like to share this file.
Step 2. Select the "Files" tab above the conversation window.
Step 3. Select "Upload" or simply drag and drop to upload either a file or folder.