Suppose you want to do a chmod 755 to all the contents of the directory /opt/application, you need to execute the following command:
chmod 755 -R /opt/application
WARNING: changing all files to 755 is not recommended!
If you want to apply 755 only to directories recursively, execute:
chmod -R a+rX *
The previous command will set file permission to a+r and directories to a+x, note the capital X.
As an alternative you can use the find command to apply the permission only to directories:
find /opt/application -type d -exec chmod 755 {} \;
If you don't use the -R option, you will only change the permissions to the directory /opt/application.
You can always execute man chmod to learn more about the usage of chmod.
