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First, you need 0.14(a) since that's where those scenes are added for the other maids, it became public yesterday.

For Leyla and Mary, you basically just need to have had sex with them, so most of the time by the time the dungeon is unlocked, you'll already be able to call them there without needing to do anything else first.

For Emily, it's a bit more complicated.
Basically, ask her about the secret room when she's cleaning your room in the morning, this will start her path towards that. Choosing the option again tells you how close you are to unlocking her and what you need to do next.
The in-game walkthrough gives some additional info if the dialogue feedback isn't enough.