please help me in my final project !

https://www.alteraforum.com/forum/attachment.php?attachmentid=6584

i have a robot which i have to measure its distance driving .

so i thought about a shaft encoder , but i dont know how to attach it phisicly to the wheel.

I attached my robot picture. i would like to get links for peripherials or their model names which can help me with distance masure.

thank you very much