Customizing Show Page Elements

I can’t seem to find out where to get guidance on if I create a new element for a, how to put it on the “show” page of the item type. I thought I might have to edit the “show-template-default.php” file, and I’m still messing around with the file to see if I can get something to work, but I keep getting this error:

Fatal error: Call to undefined function mh_year_built() in /home/arvadahi/public_html/tour/themes/curatescape/items/show-template-default.php on line 30

Is there a specific way I have to do this to properly display the element?

Thanks!
Matt

You are correct that you can edit fields in the show-template-default.php file. The error suggests you need to define the mh_year_built() function, which you would typically add to the custom.php file.