How can I give full permission to folder and subfolder

Press Ctrl+Alt+T to go to a terminal and type:

sudo mkdir /var/szDirectoryName
sudo chmod a+rwx /var/szDirectoryName

Where szDirectoryName is the name of the directory you would like, a means "all" (users) + means "add the following rights" and rwx means read, write and execute respectively...

Note: there already is such a directory in /var which all users have access to: tmp (full path: /var/tmp) which itself is symlinked to /tmp.
Beware however that all files in /tmp are deleted at boot time.

For any further information, here is a great resource on all directories in Linux.

Open Terminal

Create Directory with mkdir:

sudo mkdir /var/DirectoryName

To give all permissions to a folder give chmod -R 777:

sudo chmod -R 777 /var/DirectoryName