It is fairly easy. As far as I know almost any field can be added to advanced sarch, I will howver use price as an example.
If you go to places >>> settings you see al the fields in the form one neds to post a place online.
Select 'price' and the details will open on the left side of the screen.
Now look for the button 'advanced' at the bottom and click it. Now more options are visible.
Activate 'include this field in sorting options'.
Save it.
If I'm not mistaking 'price'' should now show up in th search tab under places >>> settings. Click it and make sure that the setting is such that it is NOT entered to the main searchbar (it is a radio button).