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, o 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, da 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 te 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 Amore to you
Let me take your hand
As we walk in the dimming light
o 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 domanda :)

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