"To learn the association" means to acquire knowledge or understanding about the relationship or connection between two or more things. Full definition
With 2 levels of spray and tone only features, your dog will quickly learn the association between his behavior and your correction; in no time you'll have a better behaved pet. (petsense.com)
The dog will quickly learn the association and stop the unwanted behavior. (doggroomers.com)
You could use any novel sound that has no previously learned association. (diamondsintheruff.com)