Hello @sarahcanada24,
Thank you for posting and welcome to the community. I am sorry to hear you are having troubles acquiring your rebate. In order to claim the rebate, you would need to have service for two consecutive months. Once two months of invoices have generated, you can then download them as PDFs from the support center. I am unsure what website you were going to but to fill out the rebate form you will need to go to https://www.hughesnetrebates.com/.
In order to view/save your invoices, please log in to the Support Center: http://supportcenter.myhughesnet.com and follow the instructions here: http://hninfo.us/viewbill. -Damian