If you already bought a ticket, you can easily see the departure point of your bus by logging in and clicking on "My tickets" (top right corner). Once logged in, you just click on the city name next to the route ID, then you will be shown where your bus departs from:
If you haven't purchased a ticket yet, you can see all the available bus stations and stops by using the search form above; PLEASE NOTE, in cases in which there are more stations and stops, the departure and arrival points may differ depending on the bus company which operates the route.
In the route search process on GetBybus.com, you will see clearly marked on each bus route whether the route has a "specific" departure point or not, this will then look similar to this in the search:
In cases in which bus departs from the main station or stop, the route will have NO "special" marker for the departure; this will then look like shown on the image when you click on the route you wish to travel on: