What can i do to stop tenant from entering my property after lease expires and they also don't leave?

You need to evict them if you want to prevent them from living their rent free.  The summar process can be technical and complicated if you have never handled it before.  I highly reccomend consulting with an attorney that has experience in this area of law.  My office routinely handles such matters and would be happy to speak with you.  I wish I could tell you it is as easy as changing the locks on the door but that is not the case.  If you do something like that you may face cvil and/or criminal penalties. Please feel free to give us a call at 203.870.6700 to speak with Attorney Christopher Hite  who can answer further questions about the process.