• Open your File Manager and navigate to the file or folder that you need to change.
• Click on the name of the file or folder  (WordPress Folder).
• Click on the Change Permissions link in the top menu of the File Manager page.
• Click on as many check boxes as you require to create the right permission. The permission numbers underneath the check boxes will update automatically.
• Click on the Change Permissions button when you are ready. The new permission level is saved and the display updated to show the modified file.

For more information visit the WordPress Codex