This is the official step-by-step given by the mod creator, Oniki.

At this time, all the brothel management is done using your Sim's smartphone. There can be only one brothel manager per world.

1. Create the business:  Click on the smartphone (or a computer) and select "Create Brothel".  

2. Hire whores:  This is probably the most difficult part unless "AlwaysAccept" is turned On.  The manager has to convince other Sims to work for him/her. Non residents Sims are really easy to convince (but it's not fun).  The manager can talk about prostitution and brothel management to increase the candidate's motivation. The effectiveness depdends on the manager's charisma and domination.  The manager can increase his/her domination over the candidate by using some interactions (Ask for, Request, Order...). Note: Just a few interactions are currently compatible with the new domination/submission system.  Candidates are more likely to accept if:  .They are WooHooer .They are unemployed .They are drug addicted .They aren't wealthy  The manager's charisma level and relationship with the candidate increase the chance of success.  Experienced candidates may request a higher wage than others in order to accept.   WooHooless Sims will probably never accept unless their relationship with the manager is highly submissive.  

3. Create a brothel:  This is optional but recommended. Brothels attract more customers and police usually don't interupt your whores will they are working.  Click on the smartphone and select "Brothels" the list of brothels should appear, but it's empty right now.  Click on "Create Brothel".  The list of available lots should appear. Non owned lots have to be bought before you can build a brothel on them. Select one of the lots. If the list is empty, this means no lot is available or they are too expensive. Remember that business's funds are used for the transaction, not the household's funds.  Back on the list of brothels. Click on the one you've just created.  There is not many things to do right now. You can rename it if your want.  Now, go to map view and click on the lot tag then select "Real Estate..." and "Build On This Lot" to create a lovely brothel.  Note: If you want to use a peviously saved lot, place it using Edit Town mode before buying the venue.  

4. Whores Assignment:  Click on the smartphone (or a computer) and select "Manage Brothel".  Click on "Employees" then "Whores".  For each whore, select the lot where he/she should go to work. You can assign them to almost any lot of the town, but you'd better choose the brothel you've just created.  Now, click on "Schedule". Each day is divided into 12 intervals of 2 hours. You have to select your whores activity for each interval. Remember that Sims have to rest and sleep. Only WooHoo and Dance activities are working at this time.  

5. Managing your brothels:  Actually, you just have to make sure your business has enough funds for maintenance (there is no janitor yet). If your business is low on funds, you can transfert funds from you household. If a brothel maintenance reachs 0, it is destroyed.  A daily (basic) report is generated at the end of each day (midnight).