How to get free space in LVM disk running Fedora 18

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I'm trying run a virtual host on my mashine using xen. For this purpose I need to create a new logical volume to be used as the virtual disk for the DomU. But vgdisplay says that I don't have any Free PE. Actually, I have about 200GB of unallocated disk space, but I don't know how to use that?

--- Volume group ---
VG Name               fedora_seafourium
System ID             
Format                lvm2
Metadata Areas        1
Metadata Sequence No  4
VG Access             read/write
VG Status             resizable
MAX LV                0
Cur LV                3
Open LV               3
Max PV                0
Cur PV                1
Act PV                1
VG Size               64,00 GiB
PE Size               4,00 MiB
Total PE              16385
Alloc PE / Size       16385 / 64,00 GiB
Free  PE / Size       0 / 0   
VG UUID               rwKWGT-Mx3q-7HaP-He20-3IDk-Gdrp-JAvK4F