Simply pick up a lemon or lime from your tree or your local green grocer, cut a slice and wipe it under your arm pit. You need to just wipe. Don't rub it in or over pump it as your single slice should be good to be reapplied morning and night for the next few days.Assuming you use lemons and limes in your kitchen for cooking and squeezing, don't set up any special routine other than finding a container for your current working deodorant lemon or lime slice. Some lemon - lime advocates wipe directly and then shower and rinse with water around 10 minutes later. Others make a small spray from the juice. If you find the slice a little irritating, try adding one part water or mixing with corn starch to make a paste. (Corn starch can help as an antiperspirant as well.)
Sweat itself doesn't actually smell. It is the bacteria that quickly reproduces when sweat is present that is responsible for your odour. Other factors that contribute are of course diet and your environment. Lemons and limes smell good and also contain citric acid. It is the citric acid that retards bacterial growth and stops your your underarm odour. Most bacteria simply don't like an acidic environment.
Be careful of applying this deodorant when you have just shaved.