Help me change my ip address please?

i was triyng to change my ip address i read that i need to login my router which i did then release the ip and unplug my router and modem for 8 hours...... i released my ip but plugged my modem and router back in 6 hours later my ip address didnt change was it because i only waited 6 hours not 8? please what are other methods to change a persons ip address cause my ip didn't change? thx