How to add songs to your iphone from a new computer?

I got a new laptop, and I synced my iPhone to it. Now it stores my iPhone backups and my songs that are already in the phone is not deleted. But I noticed that songs from my new library(in my new laptop) isn't transferred to my iPhone. What do I do if I want to start adding songs from my new laptop to my iPhone? Detailed instructions will be appreciated, thanks in advance! X

Is a used IPhone 5 worth $400?

So I was going through EBay and saw that most "used" IPhone 5's (Not talking about the 5c or the 5s) are about $400.Is that a reasonable price? Or should I get the 4s?
BQ: is the iPhone 5 worth the camera and extra half inch length?

IPhone 4 Verizon Wi-Fi grayed out?

A couple days ago I bought an iPhone 4 from my friend who had an iPhone he said was reported lost and then he found it again while he had already purchased a new one. It also had water damage a pretty long time ago and will not play any music but the phone still works perfectly. I have done research and tried literally almost everything on the internet to try to fix it, except taking it apart, which I will be doing tomorrow. The remedies like heating it up won't work or restoring it. Will taking the sim card out of the phone fix the problem?

Is it legal to use a blacklist Iphone?

I accidentally bought a blacklist Iphone 5 (I think it might be stolen). Can I use it legally if I just use it as a mp3 or an electrical device without making phone calls? Do phone carriers or polices know if I keep the phone in my hand?

Sad for not getting anything for Christmas?

I really don't think I should be not happy for not getting anything for Christmas. I have a phone (mind you not something expensive like an iPhone), and a cheap old laptop which works. My mom is a single mother and my brother is in first year university. My brother has an expensive laptop ($1300) an iPhone and now he got a new iPad air ($700). He says he needed the laptop a year ago for university when the year started (it now has), and now he says he needs an iPad for taking notes… Which is what he said the laptop was for… My mother does what she can, we're not rich but, we have a roof over our heads and food to eat. I have a phone and a laptop that works. I don't know why I feel down about not getting any presents because I really don't need anything else… Maybe its just because I see my brother getting anything he asks for (if he says its for "school") .

It just sucks to see everyone at school with new stuff and when they ask me what I got I always say nothing.

Added (1). I know I should be greatful for what I DO have, which I'm… But this just sucks… :/