Use according to package.  Pack of 3.  Apply to back of neck directly on the skin in one spot or two spots super close to each other.  
 
Watch your pets skin, depends on your pets sensitivity when using this product.  Don't guess on the pets weight.  Weigh pet before ordering.  Also, Dede recommends applying 3 days before or after a bath at MINIMUM.  Don't bathe your pet then put it on.  It's not worth it not working.
 
Oils move around the body with the oils on the body in tact.  If you bathed your pet, you washed those oils away. 
 
Read the packaging.
 
Kills all life stages of fleas.
 
Dede uses this on her pets monthly or she gets a pill called comfortis from her Veterinarian.