Sharing a folder with a channel gives the rest of your team access to your documents.
In the desktop or web app, go to the Files tab in your channel of choice. Click Add cloud storage, then select the service you want. If you haven't done so already, you'll need to sign in to your account to access your files.
Once you see your folders, pick the one you'd like to share with the channel. (All you OneDrive users stay tuned—support for adding folders from your OneDrive account is coming soon.)
FYI, sharing a folder won't automatically grant access to everyone in your team. You'll need to do that through your cloud storage provider's website.
Note: Contact your IT admin if cloud storage options don't appear.