Go to the 'verbs' tab for whatever object you think the player might try to smell. Click it.
On this page, you will see an +Add button near the top. Click it.
A box will pop-up and you need to type in that box 'smell' (or at least part of the word) at which point you should see an already built-in 'smell; sniff' clickable section pop-up. Click that. Or just go ahead and type --> smell; sniff and click 'OK'.
This will add that verb to this object. You can then double click the smell; sniff that was added to the box at the top and add whatever script you want to add when the player tries to sniff or smell the object in question. Just select a print message script and print whatever message is appropriate. Note: if you do not add smell; sniff as a verb, you will get the built in response 'You sniff, but don't smell much' (or something like that). If you tried to type in 'pummel spoiled milk' (or some other verb that is not built-in) you would get 'I don't understand your command' response (which is built-in as a response to unrecognized verbs).
All of those verbs you mentioned are built-in already (and thus recognized) and have a built-in response. This method above is what I would suggest to override the built-in responses. There is an alternate method for universally changing built-in verb responses, but going that route could lead to problems if you happen to mess up!
Good luck! Ask if you need questions!