Mailing to to different state??

I wanna send a celll phone I bought for my cousin for his birthday..
one problem this is my first time mailing anything what do I have to do??? and he lives in another state so I will be from here california to pennsylvania..
can someone give step by...

step intrustions thanks ..

Your best bet would be to bring the cellphone to the post office, they will weigh it and tell you how many stamps you need to put on the envelope and you can purchase a bubble wrap envelope from them to send it in also to make sure it get's their safe.