The bookings you just manually entered into the system will not get emails asking for their upcoming payment or security deposit. You have to actually schedule payments and security deposits for them in the system, which means you'll have to call them and ask for their credit card by phone (or ask for it by email).
You'll need to email each of your upcoming guests for their payment info outside of the system, using your own email program.
In the future, we be have a 'scheduled reminders' feature where you can email them using the system to ask for the second payment and/or security deposit. For the time being, you have to contact them yourself and then enter those payments in the system manually.
To enter the second payment, either ask for their credit card info and enter it as a scheduled payment. Or collect the second payment immediately if their due date is already here.