Doing this without the permission of the WIFI hotspot Administrator (or owner of the router) is illegal. If this is your home WIFI network, then you can ask the one who set it up for the password or Network Key. If the password has been forgotten and it is a home WIFI network, then you can comment below with the model number of the wireless router and we will advise as to how you can reset it and then set it up afresh afresh. You will then be alowed to change the current forgotten password.