Hint with the stroller. Make sure the arrow on the handle is straight up and down (it says which color is to be used with the stroller). Then give it a good push. Half the time I couldn't get the dumb thing latched in, but it sits pretty snugly in the stroller without the latch if you're running into somewhere quickly. For a whole day at the mall, I bothered getting it latched, but to run into the grocery store, I usually left it unlatched unless I got it in the first 2 or 3 times.

Peter figured out the trick.