Hi Nilesh,
You need to have a local variable, let's called AreFieldsEditable of the type Boolean.
This will control if the fields are editable or not, so it will start false has you want the fields to be disabled at first.

Then you want to have your input, button and checkbox to only be editable if that variable is True. So for each one of them (input, button and checkbox), locate the property Enabled and set its value to AreFieldsEditable:

Then on the action linked to the button Update, you just set the AreFieldsEditable variable to True, to enable all fields:

And that's it.
Hope it helps.
Regards,
João