Expand space available to Linux OS

I cloned a VM from a template.

The template had a single 40GB virtual disk.

The template had a /tmp directory 5GB is size

I went into vsphere client and made the virtual disk 100GB.  There is still only one virtual disk

After provisioning, the /tmp directory is still 5GB in size.

df -h still shows all the original directories at their original size.

What steps should I take to on partition, volume, filesystem, etc. to allow the /tmp directory to be expanded to 50GB?

File system is ext4 and OS is Centos 6

Thanks!