Can someone explain the new moon soundtrack and how it fits in ?

I don't really understand the question. It doesn't really make sense.

The New Moon soundtrack, oder any soundtack, for that matter, is a collection of lyrical songs that sort of fit with the scene it's put with.

I'll use Meet Me on the Equinox, Von Death Cab for Cutie, for an example since it's the "main" song for New Moon just like "Decode" was for Twilight. Meet Me on the Equinoxwas put in the credits at the end of the movie. If Du listen closely to the words, you'll understand that the lyrics say what the movie is about. I'm not going to go through every single song, but I'll give an example of what I mean...

An excerpt of the lyrics:

Meet me on the Equinox
Meet me half way
When the sun is perched at it's highest peek
In the middle of the day

Let me give my Liebe to you
Let me take your hand
As we walk in the dimming light
oder darling understand

That everything, everything ends

"When the sun is perched at it's highest peek
In the middle of the day" is signifying the clock tower in Italy. It's noon hence the "middle of the day". Bella is trying to meet Edward there to tell him that she's alive. To meet him halfway.

Some of the songs on the New Moon Soundtrack weren't as fitting, but then again, some were. Some songs were placed in weird positions like Muse's I Belong to You, but that's okay.

Hope this answered your Frage :)

1."Meet Me on the Equinox" Von Death Cab for Cutie Credits 3:44
2 "Friends" Von Band of Skulls Bella rides a motorcycle with a stranger 3:09
3 "Hearing Damage" Von Thom Yorke Victoria escapes the wolf pack 5:04
4 "Possibility" Von Lykke Li Bella sits and thinks while months go Von 5:06
5 "A White Demon Liebe Song" Von The Killers Credits 3:34
6 "Satellite Heart" Von Anya yachthafen, marina Edward drives Bella Home after her birthday party 3:33
7 "I Belong to You" [New Moon Remix] Von Muse Bella and Jessica go to the Filme 3:12
8 "Rosyln" Von Bon Iver and St. Vincent Edward breaks up with Bella 4:49
9 "Done All Wrong" Von Black Rebel Motorcycle Club Members from the wolf pack take Bella to Emily's house 2:49
10 "Monsters" Von Hurricane Bells Edward arrives at school 3:16
11 "The violett Hour" Von Sea wolf Bella's birthday party 3:32
12 "Shooting the Moon" Von OK Go Bella and Jacob spend time in his garage 3:18
13 "Slow Life" Von Grizzly bär featuring Victoria Legrand Bella underwater after she jumps off the cliff 4:21
14 "No Sound But the Wind" Von Editors Edward drives Bella Home from the Cullens' house after the vote 3:48
15 "New Moon (The Meadow)" Von Alexandre Desplat
16 "Solar Midnite" Von Lupe Fiasco[20] - Bella, Jacob and Mike at the Filme
17 "All I Believe In" Von The Magic Numbers - Bella and Jacob fixing Motorräder
18 "Die Fledermaus" - Duettino: Ach, ich darf nicht hin zu dir" Von APM Orchestra[20] - Edward, Bella, Alice, and Jane in an elevator