Do you mean setting “sort by alphabetical order” for a given category? If that’s the case, that might not be possible… The /filter page will look like this:
https://meta.discourse.org/filter?q=order%3Aactivity-asc
We’ll @ mention you here when we’ve got this feature merged and deployed for you. Setting a bookmark to remind 
Perhaps your admins can try it out and see if it’ll work. As mentioned in the other topic, a possible use-case is that you can use the filter link, e.g. https://meta.discourse.org/filter?q=order%3Aactivity-asc and add it to the sidebar.