Introducing a New Cat to My Current Cat?

I just adopted a rescue cat who is 5 months old. Right now I have a 11 month old cat who I've had since he was 4 weeks old. I have my new cat in my room. He was hiding under the bed for almost the whole day. He started coming out and loving on me, but is still a bit skittish. My current cat meanwhile is in the living room acting normal even though he knows about the new kitten. Anyway I switched rooms and put them in the opposite rooms. My new kitten kept meowing non stop and walking around. Why was that? My current cat kept meowing at the door to come in so I thought he wanted to meet him.

I opened the door to let him in while the new cat was in my arms. He hissed a bit, but then kind of sat there and made that chirping noise and then walked away. Then I had them face to face and the new kitten just kept meowing and my current cat was hissing. Please help. How do I do this transition? It's stessing me out and I really don't want to give my new kitten away because the rescue group said he has jumped house to house. I really want this to work so badly and give them both a good life. Any suggestions?

By Jessica s