Club boards, Reddit, and private Facebook groups are the usual places. Keep it discreet. The street stays with you.
Club boards such as SLS, SDC, and Kasidie
Hosts often post where their guests already have a profile. Pineapple Play Date is not part of those sites, and this page is not their rulebook.
On a public board, use the apply link. Strangers apply, and you approve them. Keep the private invite for people you already know, and send it by text or DM. One post for the night. Name the format and say it is a private party for couples. Leave the street out. Do not upload photos of real guests. If a moderator asks for a change, make the change.
Reddit
Use a community that already talks about lifestyle parties. Read what that community asks of a host before you post.
Put the city or region, the night, and the format in the title. Post the apply link so people can ask to join. Do not put a private invite link in a public thread. This is a party for couples, not a personal ad. No street. No face photos. One post is enough. Answer in the thread instead of copying the same note into every community you can find.
Private Facebook groups
A private group has an admin. If you are new there, ask before you drop an event.
Post the apply link with a graphic from the apply set. People who want in apply, and you approve them. Send the private invite only by message to someone you already know. Do not add them yourself. Keep the street off the post. Use a picture you would still show if a hotel printed it.