Sharing from Windows Explorer
You can create a shared link from within Windows to either a file or a folder.
You can do this by browsing within Windows explorer to your OneDrive folder and right-clicking on the file or folder and choosing the Share menu item (with the blue cloud next to it). In the subsequent Share Link dialog you can enter;
Sharing from the Web Interface
You can share a folder by going to the system tray and left clicking on the blue cloud icon then choosing View Online. From the list of folders click on the share icon to bring up the same Share Link dialog above.
Synchronising a shared folder with PC
You can sync a folder someone has shared with you to your windows PC by going to the system tray and left clicking on the blue cloud icon then choosing View Online.
Then click on the Shared folders in the left hand navigation menu.
Click on the folder you would like to synchronise with your PC, this will open the folder in a new window. From here click the sync icon.
Sharing via Teams
Sharing and collaborating on files with colleagues is perhaps best achieved by creating a Team (or a channel in an existing Team) and uploading the files into the files section of the Team. More information on this can be found here Sharing files with Teams
Request Files
OneDrive also offers a “Dropbox” type functionality where you can provide a user with a link to upload content into.
Microsoft provides pretty comprehensive instructions here: Create a file request