How get value from one field and assign to another field

How get value from one field and assign to another field?For now I am able to get Id from one field and assign to another field but I am not getting the value,Can plx suggest how to do it?

Vicky,

Can you give a little more information about what you’re trying to do? How are you getting the id from one field and assigning it to another? It might make sense for you to use an update field on row action