Maybe if you posted a link for the encoder so we can look at the datasheet we might be able to help.
or you could just Google "arduino rotary encoder" to find this
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thank you updated my post,now my sketch looks neat and tidy and regarding encoder i googled it but the one i have is very different , still i managed to get one that looks similar like mine
before using encoder i wanna know how to change lcd page every 10 seconds, can you help me with the sketch?