how often depends on the conditions you ride in. more dirt/dust in the air more you need to clean it. to clean it go to your local bike shop and buy the cleaning fuild and air filter oil.
knock off large bits of dirt/bugs/small birds so on...
apply cleaning fuild
remove rest of dirt/bugs
leave to dry or gently blow down with compressed air
top tip, apply a small amount of grease on the base of the air filter, helps seal it to the air box.
apply air filter oil
wait
apply some more
leave to settle excess to drip off
put back on bike
I've just got one today and it says
"Service filter every 50,000/100,000 miles"
Or sooner under extreme dusty conditions.
Then it says "To service: Soak in K&N filter cleaner, rinse with water, dry completely(do not use compressed air), re oil with K&N filter oil"
I like your avatar wesleyjohn