The usual channel is WhatsApp, using the number listed in the ad. A short first message is enough: introduce yourself, say which day and which slot interests you, and wait for confirmation. Replies come fast in the afternoon and considerably slower in the small hours, so a delay doesn't amount to a no; the schedule is simply organized in blocks.
With so many active ads, filtering matters more than in other neighborhoods. Read the whole text before writing: that's where it says whether she hosts in her apartment, travels to you or does both, and which hours she covers. The profiles with their own photos, a description written by hand and updated availability are the ones that later reply just as seriously.
The range of offerings is broad too. Some escorts work short meetings and others prefer long dates, with time to talk; there's massage, companionship for a dinner out and the close-treatment format many look for under the initials GFE. Each one defines her own repertoire and puts it in writing, so there's no need to negotiate anything by message.
Once the date is confirmed, the rest is punctuality and common sense. Let her know if you'll be late, stick to the agreed slot and don't turn up unannounced: in lived-in buildings that makes everyone uncomfortable. If your plan changes, write beforehand instead of disappearing. That orderly back-and-forth is what gets you seen again without any trouble.