I agree with what Leasha said. I found it awkward at first too with DS1 but by the time DS2 was born I was using it with ease.

There are two things to remember - firstly, that babies are comfortable in the oddest positions. And secondly - bottom first and bum on seam. Also put the baby/infant in bottom first, and make sure they go on the seam. So in the lying position, make sure the baby is positioned along the seam. In the kangaroo carry (or sitting) position (down the track), the bottom still goes in first and they kind of sit bottom down on the seam with legs higher than bum. It looks squishy and uncomfortable but they love it - I suspect it's very womb-like for them.

Keep at it - it will get easier and it's well worth it. A sling is so much easier when you go out, it's a life-saver for settling babies, and it's really good for them (and you). Babies who are worn cry less which is a huge bonus.

Oh, one other thing - if you have a teddy or doll which is about baby-sized, it's a good idea to practice with that a few times so you can get the hang of it without upsetting your little one.