I'm going to answer the original question, and also keep in the previous "answer", which is actually procedure for horse breeding.
First off, if you don't know of the birds and the bees, stop reading and go live your life.
If you do know, and would like to read further, continue.
First off, "How do you mate with a horse?", would suggest, a human, mating with a horse.
In short, this is not possible, biologically. Though a human and horse can physically copulate, however dangerous it may be, the DNA of horse and human are simply not compatible.
Legally, any sexual act between human and animal of any other species is generally illegal or prohibited in most countries, sometimes considered animal cruelty.
Simply put, horses and humans have no reason to mate, nor should they.
As for how one would mate a horse, or arrange breeding, read on.
Some of the following information cannot be verified as accurate by the latest user. The following information was part of a previous answer to this question, and has merely been improved to be grammatically correct, and easier to read.
First thing to consider when chosing to breed equines is a specific breed and a colour, if such is desired. If you desire a specific color, both the mare and stallion should be the same colour, however, there may be dormant genes that could potentially change physical appearance. Looking back in the liniage will help.
Once plans have been arranged, wait for the mare to come into season. Optionally, having both stallion and mare in the same area for a period of time beforehand, a week or more if desired, may aid in the two growing accustomed to the other.
Once the mare has come into season and is receptive to the male, nature can take its course. If the female will not stand for the stallion, she is simply not receptive and ready. It is not necessary to force her. Consult your local veterinarian if you have further questions.
a Morgan Horse :P
the same way regular horse mate
no
No.
Nope
It depends on what markings the horse and the donkey have.
howrse
I don't think so, only a mare can mate with a stallion. _ThehorseGal&Advisor
Yes.
Monomagus
A horse and a cow can NOT mate. There fore there is no name for a nonexistent baby.
When a horse and a human mate and their chromosones thingys match.