1.Log into your Plesk Control Panel.
2.Go to the Domains tab, and then click your domain.
3.Go to the Websites & Domains tab.
4.Click FTP Access
5.Click Create Additional FTP Account.
Complete the on-screen fields, and then click OK.
6.Download FTP software from here https://filezilla-project.org/download.php
Install the FTP software and run
7.Please open "File" menu in Filezilla and Select "Site manager".
8.Click on "New Site" Button and enter your domain name in "Hostname" Field
9.Select "FTP -File Transfer Protocol" in "Protocol" Option
10.Select 'Use plain FTP" in "Encryption" Option
11.Change "Logon Type" to "Normal" and enter credentials in respective fields and click "connect"
You have to upload files to your hosting root foder, For Windows Hosting it will be 'httpdocs'.
Change to that directory by doubleclicking its name in the folder portion of the right window pane (the "Remote Site" window pane). FileZilla will open that folder and show you its contents in the files portion of the Remote Site window pane.
Next, locate the file that you wish to upload in the left window pane (the "Local Site" pane). Both window panes behave mostly like a Windows Explorer windows, so navigating them should not be unduly hard. Once you have located the file you wish to upload, doubleclick it to upload it to your website. Alternatively, you can drag that file from the left window pane to the right window pane. The file will be uploaded to the folder that is currently open on the right window pane, so make sure you have changed to the directory you want before dragging the file there.
As FileZilla proceeds to upload your file to your site, you should be able to see the upload progress in the bottommost window pane in FileZilla. When the upload has completed, you can disconnect from your website. Do this by clicking the "Server" menu followed by the "Disconnect" item.