That's not supported yet, unless you want to go into the relay view and manually select the relays you're interested in (after the search). We want to support that on the syntax level soon. Just tracked an issue for it.

GitHub
feat: support relay: filter for user-specified search relays · Issue #171 · dergigi/ants
Summary Support relay:<url> syntax in search queries so users can target specific relays. Example is:longform relay:pyramid.fiatjaf.com Should sear...