There are many tutorials about this, but I decided to have a go at writing a very brief how-to. These methods described can be used with my boxes or any other pose boxes.

The main problem you may have is trying to get these to look as the pictures do. When you position two sims close to one another, one sim may fly off and be up in the air... to get the poses to look the way they do in the picture, you must use an omsp along with your cheats.

Most of the poses are designed to "snap" together using a simple cheat and an omsp. One More Slot Package.
I recommend this pack here. Yes there are a lot, but if you get the collection file as well, it makes browsing so much easier.
The other omsp's come in handy for more complicated poses, like shifting the sim up or down... example: if you have a floor pose and you want it on a bed.

If you didn't download the collection file, you can find the omsp's in the Counters > Misc  section of your catalog.

Method #1:
This method only requires "moveobjects on" and a regular omsp.  You can also use "boolprop allow45degreeangleofrotation true". For easy sim posing, use the basic game omsp... it will be the one that is black with no number in the middle.
  A) Open up your cheat menu Shift > Ctrl > C   and type "moveobjects on"
  B) Now, grab one of your sims and position them on top of the black omsp.
  C) Now grab the side of the omsp and position it close to the other sim, it should 'snap' close.
  D) Making adjustments: if the sim is backwards or sideways, click and hold the omsp and use the <  or  > keys to rotate your sim until they face the correct way.

Method #2:
Okay, so you tried method 1 and it still didn't look right. This method is the one I use the most and requires "moveobjects on", "boolprop snapobjectstogrid false", and your basic omsp. You can also use "boolprop allow45degreeangleofrotation true". This is used to get the sims a little closer or a little further away from each other.
  A) Open up your cheat menu  Shift > Ctrl > C and type your two cheats, "moveobjects on" and "boolprop snapobjectstogrid false".
  B) Grab your omsp, place it on the floor, and then position one of your sims on top of it.
  C) Grab the side of the omsp, you will notice that now the omsp with your sim on top doesn't 'snap' to grid but you can slide it anywhere.
  D) Position the omsp as close, or as far as you need towards the other sim. Remember to make adjustments if you need to by rotating, <  or  > keys.

Other methods:
I have read on various forums about other methods that work. I haven't tried any of these but if they work better for you, then that's great! Try this one