make an instructable and then click publish select knex and one other catagory or not then type in two keywords like knex and whatever it  and slide the bar for cost( higher for alot of pieces lower for not that much) slide the difficulty bar for how hard it is to build and enter it in any contests by checking the box next to the contest picture then choose the license attribution-noncommercial-sharealike if you want to allow other people to use your design aslong as they give you credit for it. read the others for more information about license's. and thats how you post an knex ible, it takes a while for your ible to appear(up to 48 hours) and sometimes it can be rejected for copyrighted material.

You would post it just like any other instructable. If you are thinking of starting one, go on Your page (press "you" on the top right corner), then click "Instructables", and then on "Unpublished." You should see an orange box saying: "Click to start an instructable."