How do I expand my File System (Root or LVM Partition) ?

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So I bought a new hard drive to allow more space but after making a clone of my other drive and writing that to the new drive, I have all this unallocated space. So, thinking it was wise of me, I used GParted to expand the Root partition. But, it still shows in my filesystem as the original size, 27GB. What can I do to use all of my hard drive space?