How do I find the suite key in pokemon diamond?

ok im at the part in the pokemon diamond where I need to find her suite key I CANT find it please help

Hi,

Fly to Pastoria city. Go to the hotel near Lake Valor (Hotel Grand Lake) and enter. Go past the guy at the reception desk through the exit. Go directly to the left after you go through then look up and hit the A button. Then give the key to the woman in that hotel area in front of her door. When you go inside she should give you a lava cookie. Yum. A lava cookie is like a full heal it heals all status problems. The guy at the reception desk should now heal your Pokemon when you talk to him.

Good luck.

thank you so much it worked and now how do I get to the gym leader in pastoria city

I tried to do that but it would not work!!
Can You explain again how to do it??
Thanks

Actually Never Mind I Found It!!!