create an Order Form Program

Question

Hi i was task to create a Order Form(OF) Program. my company deal in construction thus the order form will be use to order the metal bar which is use to reinforce the concret wall. below is the problem i'm facing now.

when the user click on a button called "new item", it will pop me a selection of item to be included in the OF and by clicking on the item i can key in the size, quantily and other infomation. the selection will be a form showing the item. however the items how do i display them do i just show a picture, jpg. of it ? or it there a better way? after selection the item will be show in the OF which is going to be printed out.

i'm kind of lost as how should i display the items. if the item is shape as follow

               
|        |   |
|        |   |a
|____|   |

|-------|
     b

How do i make the program such that i'm able to let the user key in the length in position a and b.

can you point me in the right direction and recommand me some topic which i can read up to gain more knowledge in this area.