Extremely obvious: simply select departure airport and destination airport, a magenta line will be drawn automatically between the two showing the direct shortest route, then simply pull the magenta line to meet the waypoints/VOR you wish to select, try it for a simple flight and you will see for yourself how easy and intuitive it is. SID and STAR may be proposed depending on weather forecast.
Let me take you to a simple route as an example. First you will need to open an account a simple and fast process (free).
Then select which type of map you want to use (VFR or IFR low or high). Let’s say that for this exercise you select World Low (click on the box on the upper right corner of the screen).
Click on FLIGHTPLAN (upper left corner of the screen). In the departure box type EDDH (Hamburg - Germany.) and in the destination box ENVA (Trondheim - Norway).
A magenta line appears. Zoom in until you clearly see the first possible waypoint out of EDDH and locate ABGEB on the map, pull your magenta line on ABGEB, continue North and locate ALSIE (that happens to be on the magenta line, right click on it and your route will automatically also insert EKERN (between ABGEB and ALSIE (notice that your routing is automatically updated in the FLIGHTPLAN window upper left), follow your magenta line going North and locate AALBORG VOR, pull your magenta line on it and right click, select VOR, again all previous waypoints will be automatically inserted, up North again locate near your line NEDZA, pull the line, right click, further North still close to your line, locate UTUNA, pull, right click and observe the route between NEDZA and UTUNA being updated,
In your FLIGHTPLAN window, your FlightPlan will now read: EDDH ABGEB M852 ALS P615 NEDZA P601 UTUNA ENVA. Copy and paste in Simbrief, transfer to MSFS, within MSFS click on LOAD and SAVE, find your EDDH-ENVA FlightPlan, load and you are ready to go.