Creating routes:
1. Rent a gate at your destination airport.
2. Make sure you have at least one slot free at your departure airport (In this case Heathrow)
3. Click 'operations' then 'create route'.
4. Select your departure and destination airport.
5. Select your aircraft.
6. Choose some high price, and set frequency to 1.
7. Adjust the price to get a loadfactor of 98-100% by pressing 'update results'.
8. Click 'create route'.
Gates:
As Jayceon says, you can rent gates even if it puts you in red. The only way you can loos is to be inactive for three weeks. You can't go bankrupt.
How to rent gates with one click - OCP (One Click Purchase):
Go to the admin panel. At your right it says
Imroved OCP - disabled. Click on 'disabled' - now, whenever you press on OCP to rent a gate, the button (OCP) turns green and says 'Done'.
For more information, read on the wiki (links below).
Another good feature, which helps you understand the game is the in-game manual. To enable it go to 'Admin'. Scroll a little bit down, and at your left click 'enable in-game manual'. This will show a box with advise on each page in the game.
You can disabling it by doing the same.
Finally, a question:
What year are you in?
WikiThese articles on the wiki will also help you:
Creating your first routeHow to rent gatesTips for new usersMain page with links to every article