You can't, it's date expired. :(
By action replay or events that that come rarely
No.
its an item you bring to that rout east of the league to ge shaymin fljkfdljkfljkfdlk;dslk;lfdlkfdslfd
You have to get it from an event, but there hasn't been any event lately for Pokemon diamond/pearl. Most of the events are for platinum now, oaks letter was given out a feew weeks ago for platinum. You can keep a look out though by going to serebii.net
you don't use wifi to get the oaks letter.anyhow that's goes to get shamin. ONLY Pokemon PEARL/DIAMOND can get shamin.so how to get the oaks letter? you have to beat the elite four.then you fly to the Pokemon league go down the watterfall.NOTE! you only can get the oaks letter from pearl or diamond versions.go on Google.com to get through.! note you have to have the national pokedex.at the end you will see professer oak talk to him after that go to Google.com to find out more!!!!!!!!!! cheres
no
You can trade with someone who has Shaymin, but that's your only option. To get Shaymin, you need Oak's Letter or Action Replay.
Do not let a Pokemon hold it for it to work.go to floaroma meadow.
u need oaks letter that's where shaymin is get oaks letter.
take it to the rock up there by the Pokemon league
You don't
complete the national pokedex and go to canalave city in the pokemart and theres a man by the counter talk and he will give you give you gifts one of them may be oaks letter.