Ther are 2 methods to do this.
- From front User Interface.
- 2. From cmd.
- Locate terminal and run the below
To change all the directories to 755 (-rwxr-xr-x):
find /home/xxx/public_html -type d -exec chmod 755 {} \;
To change all the files to 644 (-rw-r--r--):
find /home/xxx/public_html -type f -exec chmod 644 {} \;