Easy:
1- First you need a bitcoin wallet address-- there are many sites where you can create a wallet address but I highly recommend you sign up at :
https://blockchain.info/wallet#
2- upload the blockchain app to your phone
3- If you are downtown you can buy bitcoin at
http://torontogold.com/bitcoin/ bring cash $20s, $50s
4- Bitcoin ATM at Torontogold scans your wallet address from your Blockchain phone app
5- You pay for the bitcoins with cash, after you are done press SEND and the ATM sends the bitcoin to your wallet. You will see a message on the ATM that says the bitcoins have been sent ( to your wallet).
6- Log into your bitcoin account from your computer to send bitcoin to backpage.com ( you can send from your phone but it's easier to copy and paste the backpage wallet address on your computer )
7-When you pay with bitcoin always make sure to enter the exact amount on the invoice!
8- If you use Torontogold call first to make sure they have enough supply of bitcoin on that day.
9-If you need help purchasing bitcoin Torontogold staff will be on hand to help you.