Apply the changes and boot into regular Centos.
Use
vgdisplay | grep "Free PE"
to view the free space and note the first value which is the number of free blocks
lvdisplay | egrep 'Path|Size'
LV Path /dev/centos/swap
LV Size 1.60 GiB
LV Path /dev/centos/root
LV Size 77.91 GiB
Note the partition name you want to expand
Now we need to extend the LV
e.g.
lvextend -l+4222 /dev/centos/root
Finally, you need to extend the xfs file system to match the partition
fsadm resize <partition to be grown>
e.g.
fsadm resize /dev/centos/root