First: keep in mind that vampirism is a rare dissease and spreads slowly. as most players are new, it is not far spread and therefore the demand is much higher then the supply.

There are two ways of getting infected.
1: get levelled up and when you find yourself in reaper's march (level 38-45 zone), go to the places where the bloodfiends spawn, at the rigth moment (night with specific moons) and get bitten. It can be done at lower level, but as they have to hit you several times, it is likely you won't survive long enough. The window they spawn at night in is only 1,5 days long and it only happens once in a while (the exact type of moons needed are still a bit unknown). So all in all it means a lot of luck.
2: get a vampire player who reached level 6 in vampirism. he can escort you to the vampire shrine in reapers march and bite you. A vampire player can only do this once every 7 days. And currently only people who transfered from pc will have level 6 vampires.

So the result is that prices are skyhigh at the moment. I expect that it will be 6-12 weeks before there will be so many vampires, that prices will be the same as on the pc (2-5k, and most guilds infect eachother for free).

At higher level, the levelling of the vampire skills goes reasonable quick. so maybe it is better to wait a bit or maybe do it on your second character.

As vampirism is a bit of a glasscanon type of effect, it might even be recommendable to not do it on your first toon. (it is glasscanon, cause it increases your magica and stamina dps significantly, but your health regen is slowed and you take a lot more fire damage, so more dps traded for less survivability)

how can u see what time it is in the game? since dont see clocks so dont know when it becomes night

There is no ingame clock. So you have to look up. It is night if you can see the two moons and the stars.

and how do they become vampires without being bitten? since someone had to be the first vampire. and he woudnt be able to get a bite

Everyone is bitten, either by another player or by the npc's that spawn in very specific places (in the three high level maps) and under very specific moons and only at night. So the first vampires contracted it from the very rare npc's. Keep in mind that all other npc's can't infect you, even if they are a vampire.

Ok so I got bit buy a vamp and have vampirism, where do you get the quest line for it