Files can be uploaded directly to a database record by utilizing the Files & Discussions feature tab within database records. Files that are uploaded to database records are automatically stored in the workspace Attachments System Folder.
You can also attach existing files from the Files & Discussions area to any database record. To attach files to a database record that already exist in your Workspace, go to Files & Discussions and check the boxes to the far-right of the files you want to attach and select the More drop-down menu. Then, select a database under Attach to Database.

A window will appear where you can begin typing the name of the record. As soon as a few letters are entered, a list of matching records will appear. Select a record where the file will attach to.

The files will now appear in the Files & Discussions tab for that database record.

Each file can be attached to multiple database records at a time, and multiple files can be attached to a single database record.