You put the camera where all good cameras go.....on your office computer. I know it offers you the opportunity to also put it on Aletta's comp as well but I don't think there is anything available for that yet or if its even planned. You can't use but one camera yet and tht seems to be the one in your office. Could be a fun addition as well for future use.
As for the evidence. Talk to Lavish, in her conversations section it should have a magnifying glass icon to discuss investigation. Have good love points with her. She should of to help. Audrey as well although she never is any help. Avoid Shiori as she offers to help but actually hurts instead. Alleta as well can help. Also hack Alleta;s computer in morning or evening after she ISN"T in her office. Just remember she works out every day before work so its a good time to skip your workout and snoop. May take more than one attempt. Usually takes me two . TIP: DO NOT GET TO 100% prior to your meeting time with daddy's little slut in your office. If you do in my game I did not get the meeting at all. However if you get to like 65% to 80% then do the meeting part and record it then after get the remaining part to 100% everything seems to work out great for you. Enjoy the results. I did.