There used to be a practice in podcasting where we would add episode numbers to our podcast titles manually by simply typing them in to our episode title, for example:
312 - How I Became a Jedi & Brought My Father Back from the Dark Side
That was ok, but now the podcast directories and in particular Apple Podcasts now have very specific labels that they use for podcast numbers to give you the same kind of ability to reference episodes but that also means no more manual typing of episode numbers into titles.
In short, it's easier and better for listeners.
When you publish an episode, it's super easy to add your episode number:
During publishing or editing an episode, navigate to Episode Number.
Type in your episode number or use the controls to choose a number.
Click Publish, Schedule, Save as Draft or Update Episode as relevant to your needs.
Remember, you do not need to type your episode number in to your podcast title.
That said, if you use Captivate Sync to send your podcast episodes to your WordPress website, maybe you would like to show the episode number in your title on your website only, in which case check out this tutorial on showing a different episode title on your website.
Note: if you import a podcast from another host where you hadn't previously added episode numbers like this, now is a great time to go through your archives and do it.