Uploading and sharing files in Microsoft Teams can be done in several ways:

In a chat or channel:

1. Click the + button in the compose box, click Attach (paperclip icon).
2. Choose Upload from this device or Attach Cloud files
3. Select the file and click Open
4. Add a message (optional) and hit Send

Alternatively:

• Drag and drop files directly into the chat or channel conversation

In the Files tab:

1. Go to the desired team/channel
2. Click the Files tab at the top
3. Select Upload > Files
4. Choose your file and click Open

Sharing options:

• Get link: Create a shareable link to the file
• Attach copy: Send a copy of the file
• Upload from OneDrive: Share files stored in OneDrive

Tips:

• Use @mentions to notify specific people about shared files
• Edit files directly in Teams using Office online apps
• Use the Files section in chats for easy access to shared files

For more details, see Microsoft's guide: Share files in Microsoft Teams