How to repartition mac mini lion server 10.7.5.

Purchased Mac Mini Server OS X 10.6 in 2010. Upgraded to OS X 10.7.5 Server Lion. This was my first time purchasing any kind of server. On setup I split the hard drive in half and didn't realize my mistake until the first half of the hard drive (about 500 GB) became full over the years. The second half (about 500 GB) is empty. I currenty have a time capsule making back ups.

How can I combine both halfs togther to tap into the unused 500 GB?