Unless you actually bought an IBM machine, it probably didn't have OS/2 installed. So you would need to actually buy OS/2, (and also a RAM upgrade, with OS/2 needing more than Windows 3.x), and if you wanted to run (16bit) Windows Apps, I believe you needed to buy the more expensive "Blue Spine" version.
I knew of a few people who got OS/2 as a pack-in with a new PC clone from a big store chain in that time (it was Escom I believe). Apparently, IBM also tried bundling as a way to increase market share.
Unless you actually bought an IBM machine, it probably didn't have OS/2 installed. So you would need to actually buy OS/2, (and also a RAM upgrade, with OS/2 needing more than Windows 3.x), and if you wanted to run (16bit) Windows Apps, I believe you needed to buy the more expensive "Blue Spine" version.