Cows mate through the act of reproduction. The female cow will go into heat every 21 days. Then the male and female cows will have sexual intercourse just like all mammals.
1 Additional Answer
Cows mate in a way similar to humans. A female cow ovulated every 21 days. When a female cow is ready to mate she gives the male cow a signal and the cow mounts himself onto her an extends his penis inside of the female.