Hi Leanne,
Sorry to hear your having difficulties here. I think I know what your refering to. When you get the "Select Bank Account" screen, and you have the 2 options of either "Use an existing QuickBooks account" or "Create a new QuickBooks account", select "Create a new QuickBooks account", then select "Use an existing QuickBooks account", you will then be able to select the account you want. Unless you select "Create a new QuickBooks account" first, then go back to "Use an existing QuickBooks account" the drop down box to select your account is greyed out like in the screen shot below. Just remember to toggle between those 2 options when you get to this screen. Hope this helps.
Regards,
Shane.