The message
from "H Ryder" contains these words:

How do you turn fresh horse manure into something that can go on the garden?
How long does it take? Thanks,

A big pile of freah manure (cubic yard plus) will get very hot for a
week or two. Also, it may contain viable seeds. Some people dislike the
smell. Those are some reasons why some people let it mature before using
it.

If you want to do that, stack it, protected from rain to prevent rain
leaching it, and wait 6 months. It will cook the seeds then cool and
begin to decompose into a crumbly dark odourless friable material.

However, if pushed, you can spread it neat on the soil during winter
months (avoiding contact with any plant stems), and leave it for worms
to take down into the soil, which they will do very quickly. You may get
a few weeds germinating but IME it's a trivial problem. Or, if you are
double digging, fork in large amounts of manure as you go. There won't
be a weed problem because they're buried too deep to germinate. I
usually use the 2nd or 3rd method, because I fetch manure in sacks
during winter, and it's just more convenient and labour-saving to
shift them only once.

When I acquire it in small amounts..such as, dropped by horses
passing the garden gate.. I just add it to the compost heap as an
activator.

Janet.