Rather than using "What's This" on the event commands screen, you have to actually click on "Show Text" and then use the function (you don't have to right-click, you can also click the "?" at the top-right and then click on something to learn about it).
As for your question, you may want to check up on bridge tutorials. In the database, you can define tile "heights" with the "Priority" setting (again, you might want to use the "What's This" function for more info). However, you can only have one priority on a tile, which is why a bridge can only be walked over or walked under, but not both.
To overcome this, you'll have to use events. Try reading
this tutorial, it should help. Good luck with it! :thumb: