I'm new to this game, and i love the shit out of it

I prob did something wrong, but i cant seem to get my "Inserter" to load up my cargo wagon on the train.
I tried every Inserter i have, i tried from both converbelts and boxes but the only pick the item up, and then hover it over the wagon.
Do i need to research something special for this?
All the best!
Spazzme