how to reinstate IP address in lenovo tab2 a10-30

I received a security message saying my wifi was being hacked and should turn off, I clicked the option to turn off. have since tried to reconnect and it says authentication problem. I then told it to forget that connection and tried to set up again but have noticed it says IP address unavailable and the authentication problem still comes up.
Anyone have an idiots quide how to re-instate IP address.

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