Your posts give me the sense that you were expecting one of these girls to give you more conversation. And maybe you were hoping for a date, and are super upset because you didn't get one.
Best way to develop interest is to try to find an activity they are doing that you can talk about and if they don't reciprocate well, look for someone else to speak with. If no one talks, that's your cue to leave.
If there is a girl sitting by herself, you can go up to her and try to talk to her and if she doesn't respond, move on. If you can go with a trusted friend who can advise you possibly at such an event, this could help.
Also, if you don't feel you are able to attract what you desire, consider things to help yourself out. Could you exercise more, study and become more intelligent, find hobbies and groups that like to do the same hobbies as you such as board games? Doing these type of things will help you develop as a person and will help you level with people where you aren't leveling with them now. It will help you know intuitively yourself when you need to move on, stand up for yourself if being disrespected, and help with when something positive is occurring to know how to accept it. Being able to accept rejection, platonic connections only, and a building up of dates will help you a lot too.