Same time as any other election. Spring primary and November general. Will be on the same ballot as mayoral race, plus maybe a ballot measure and a special election if somebody resigns.

To add to other answers:

The date of the primary is not officially set yet.

When it is, you'll find it here:

https://www.vote.pa.gov/about-elections/pages/election-calendar.aspx

and here:

https://ballotpedia.org/Pennsylvania_elections,_2023

PA Judicial primaries are especially important, as candidates can “cross file.” You don't need to be a member of a party to appear on that party's ballot.

Especially in a crowded field, cross-filed candidates “sneak through” and win the other party's primary.

Even before the primary, you can help judicial candidates by signing candidate petitions to get them on the primary ballot. By stepping forward to do this, that's one less signature those candidates need to “chase.”

There are often local “signing parties” you can attend early in the year, and if there aren't, your county party will have petitions at their office (which is typically in your county seat) or a local volunteer may be willing to come by your home.

To get in touch with your local party, Google <your county name> <your party name> , e.g., Centre County Democrats

Major parties select their candidates in the May primary. General is on the Tuesday in November.

Important to remember that this is also a school board election year. The R's will redouble their efforts to take full control of local public education with their CRT/indoctrination/anti-kid bullshit.