This mod adds increasingly intense sexual exploitation to both the Fort and Cottonwood Cove. Once you arrive, Legionaries will start harrassing you. At first they're just curious, but very soon they'll be demanding sex. You can fight them off, but the longer you're there, the more submissive your options become. They are more aggressive at the Fort.
(Of course you can attack them whenever you like outside these encounters!)
Depending on your responses and their whims, some of these encounters will be rapes; be careful, as these cause damage.
Eventually they'll capture you, remove your clothes and weapons, and put you in the slave pen-- in training to be a slave. A couple of Legionaries will give you some basic education in proper slave behavior, and also offer a way out... if you fuck enough legionaries.
Once you've serviced them enough, you can wander the Fort (but as you have an exploding collar it's not a great idea to leave). At this point even Dale Barton and Siri consider you fair game.
If you want to accelerate your capture, try one of these options: start a conversation with Otho or Antony and be abusive; or go around naked (which increase the chances of capture).
Once captured, you can earn release by fucking enough legionaries. Or, talk to the blacksmith, the only person willing to help you out (but if you are recaptured, he cannot help you again).
If you prefer to become a permanent Legion slave, talk to Vulpes or Lucius in Caesar's tent. You will still have to make your quota of legionaries, but after that you can move around the Wasteland, and your master will have several missions for you.
If Veronica or Cass are with you, you can often suggest that they be used in your place.
If you have my msexVeronica mod installed, more interaction is possible. If Veronica or Cass is a sub, she'll let you whore her out; if she's neither domme nor sub she will be offended if you do so and may even leave you. If she's your domme or owner she'll be amused by the whole slavery thing and order you to cooperate. (Also, she won't take you out of the Fort.) You can also talk to her about your predicament.
This mod is designed for female Couriers. (A male version would either be not very exciting, or not lore-compatible.)
You'll need Sexout and Sexout Common Resources.
You'll also need the msexBase.esm file and the 7z resources from my companion D/s mod: http://www.loverslab.com/files/file/35-msex-veronica-ds/ . You don't need the msexVeronica.esp file, but the two mods do work together, as described above.
If you have Sexout Tryout installed, turn the frequency of Legion molestation down to 0. (I don't have it myself, but this is the report of people who do.)