Can I convert Kiddicarrier jogger to a bike trailer?
If you’re transporting kids then I’d stick with the manufacturer’s conversion kit if they have one. If they don’t have one, then I’d sell your trolley and buy one that does have a conversion kit. You don’t want to explain to your spouse or parents why their kid/grandkid died in a horrific accident when your DIY trailer hack came apart in a busy intersection.  

Otherwise, if you’re carrying cargo the DIY conversion isn’t hard. You just need to first decide if you want to put the hitch on one of the axles or tow from the seatpost or rear rack. There’s advantages and disadvantages to both. I have a question of here that lays it out. 

Fabricating and mounting a drawbar isn’t too hard. The folks at the hardware store can help you bend pipe or conduit and sell you pipe clamps to mount the drawbar. 

Then you need to buy a quick release or make your own. They’re not hard to make but hard to make well. They sell kits on amazon.