I bought a used older model It is a huffy aerocruiser bicycle trailer. has no instructions on how to assemble them onto your existing bike.where does it get attached to and what hardware do you newed to go with it my came with 2 cotter pins thanks

Thank you I as well bought a used one w/o instruction but I am using it for a dog cart...thank you for the help...

Ktbird80, I read it twice and still doesnt make much sense since I am a picture guy, If its okay and If I can request, can you please share some pictures so that I can better understand it?

While I am no expert, I have a huffy aerocruiser. I also purchase mine second hand, but the woman who sold it to me was excellent on giving instructions at pick-up time! There should have been a peice that fits over the stem of your bike seat and and arm type thing that runs from bike seat piece to the stroller itself. There should also be two clips, a wheel, and a handle. To assemble for bike use, remove your bike seat and place the bike seat adapter piece on the stem of the bike seat then replace bike seat. Use one clip to attach arm to bike seat adapter thing. Use the other clip to attach the arm to the stroller (where the front wheel would go, wheel removed). The bike seat adapter thing remains on the stem of your seat and you just remove the clip that holds the arm to the bike seat when not using the trailer.
To use for jogging, remove the arm and replace the wheel. Slide handle into place and use two clips to hold handle on.
If this requires clarification, please let me know! I may not have made it that clear. I would be happy to take some pictures if it would help!
Best of luck and enjoy your new stroller!