I think he knows what everyone normally does (riveting and welding) but bending tubing like that can really be stupid simple with not that much hardware. You could use a machine but that is very expensive and probably not what you are looking for. The method I think is most appropriate is what this gentlemen did
https://www.youtube.com/watch?v=vguWbHxzG98 . This is just a bigger verson of this http://www.lowes.com/pd_472951-295-MCB1-2_4294653949__?productId=50114251&Ns=p_product_qty _sales_dollar|1&pl=1¤tURL=%3FNs%3Dp_product_ qty_sales_dollar%7C1&facetInfo= . If you really are very dirt poor with little resources get a piece of pipe 2in in diameter or larger place it in a vice. Then clamp the end of your tubing to the side now as you pull on the other end of the material it will bend around the pipe. Note that this will not be easy it will take a lot of force but has to be slow and controlled force or you will end up with a sub par bend. It is not how you are supposed to do it but it will definitely work. Best of luck to you.