Old Spice has several deodorant products. However, the basic method of application of each one is consistent. Proper application prevents sweat and helps maintain a pleasant odor.
Before applying the product, take a shower, or at least wash the armpits. Cleaning rinses away existing sweat and odors. Otherwise, the product only masks these problems.
Twist and apply
Typical Old Spice deodorants have a twist feature at the bottom used to push the product up through holes at the top. Twist a couple times and check the dispenser holes. When adequate product is released, run the deodorant up and down each armpit twice.
Sniff and re-apply
It is better to start with a moderate amount to avoid excessive application, which creates a strong smell. If the initial application is too light, twist again and reapply.