Adding chunks

I'm a long-time developer who has suddenly been handed a DBA hat to wear. I understand I should make a link to some raw disk space and use onmonitor to add the chunk. What I'm unclear on is allocating the raw space, and I apologize in advance since this may be more of an OS (AIX 4.3) question than an IDS question. I can see our physical volumes with lspv. Looking at one of the disks in the volume group set aside for IDS with "lslv -p hdisk2" command, I see a bunch of "USED" sectors(pages? I'm not sure exactly) and a number of free ones. Instead of guessing what I should do, I'll just ask. What's my next step? Thanks in advance,