1. Pay the extra $5-10 for a seat assignment.  That way, you can choose a Windows or Aisle.  Otherwise, you get whatever WestJet assigns, which includes middle seats.
2. Download the WestJet app and register.
3. Check in via the app before leaving for the airport.  You can do this up to 24 hrs ahead of time.
4. If you have to check a bag, arrive 90 min before departure.  Otherwise, 60-90 minutes is enough.  Calgary is not a large airport.
5. If you check in via the app, that is you boarding pass.  You don't need to print one.
6. Know requirements for entering the terminal.  You'll need a government issues ID.  I assume Canada has the liquid restriction also.  Pointless, but you sill have to comply.
8. Once you enter the terminal, go directly to the gate to make sure that's still the right gate.  You can also check the displays, they're everywhere.  If you have time, now you can walk around.
9. Be at the gate 40 minutes before departure or 10 minutes before boarding time, whichever is earlier.
10. Board with you Group/Row.

Traveling alone at 14 is not uncommon.  I started even younger.