When you open the main page of the software, choose your keyboard, and click on Key Bindings.
As an example, we have chosen the key 0, then on the upper right screen choose Key instead of FN+0, if you would like to reproduce this function without pressing Fn+the following key.
Then go to Action and click on Default and a drop menu will show up, then choose Launch Application.
Below you will see Choose Application and then choose the one from your desktop (We used Twitch as example) when you verify that you have chosen it, it will show .EXE of the app, in this example Twitch.exe and then click on the Save Changes.
Whenever you click the assigned key, the application will start.
If you want to change the Key Binding, go under Action and click and revert to default.
Afterwards, you can choose which key you want to use to assign the said application to.
As a reminder, the key binding isn't transferable through profiles, so you would need to set it up again if you change from one of the four profiles.