Attention! This guide is for File Manager on cpanel only. If you are using any other control panel, please find the corresponding guide.
For uploading file:
1) Click on File Manager icon in cpanel.

2) Here you can choose the desired directory for uploading. For example, double click on the public_html folder.

3) Click on upload.

4) Select the file to be uploaded.
Note: You can check the Overwrite existing files box if the files need to be overwritten.