If you are using GOG GALAXY, then please open the GOG GALAXY application, click the game, click on Customization button -> Manage Installation -> Configure:
Enable Launch parameters:
Click on Duplicate:
Now in second group do not change "File 2". Instead add arguments you want to run your game with for example: -force-opengl
And change label to something more convenient:
Press Ok. Now check again the Customization button and check if you have there Additional executables section:
If you are not using GOG GALAXY, please go to the game installation folder (by default: C:\GOG Games\GAMETITLEHERE). Once in there right-click on Launch <gametitle>, and select properties. In Properties window, switch to Shortcut tab, and here add required parameter at the end of Target field following the example: -force-opengl
If the game is installed to default installation folder, then the Target field should look like this:
"C:\GOG Games\<game folder>\<gametitle>_x64.exe" -force-opengl
After that press Ok, to apply settings and start the game using the modified shortcut. If you are using a desktop shortcut for this game, please replace it with this one.
For example: