In Plesk Control panel the "File Manager" is used to upload, remove and organize all your website files.
1) Login to Plesk control panel.
2) Click on "Websites & Domains".
3) Click on "File Manager".
Note: Your main website's files are listed under "httpdocs".
4) Click on "Upload Files" for uploading files
* Click on "New" for Create new file and directory
* Click on "Remove" for remove a file or directory
* Click on "More" for more actions
OR use FTP credentials for managing website files. Please follow the below steps