there are many ways. One of them is:
You can do it simply in winbox by check box by one click
in src address or dst addres (that depends on rule you are about to use) click on small box located on the left of address field, then appears exclamation mark (!) in there. This does mean that rule will work only with ip addressess whose do not satisfy that condition, in this specific case for example you want bypass the rule for a specific IP address lets say 10.0.0.1, then you should have that address in rule and exclamation mark before it in the box. That does mean IF IT IS NOT 10.0.0.1 THEN DO THE RULE. In case 10.0.0.1 rule is bypassed.
Hope that helps