The Red court venom

[Deimos]

How affects a human? Also, besides that I can tag the consequence for free, I`m not sure how to roleplay it. Last session,  a player gets kissed by a RCV and gets infected. I compel his consequence "Addicted" to block another player from doing spells. Was that right?

[Taran]

Yeah, you compel the consequence and the player can choose to turn it down with a fp.  Were you compelling the same character who cast the spells?  or another character to hinder the spellcaster?

In any case, you kind of use it as the RCV's hold over the addicted.  "I won't give you your next fix if you don't do "X,Y,Z".  Or maybe they need their fix and can't act because they're going into withdrawal...  You know, be creative.

I don't understand the first question.  How does it affect a human? 

[Deimos]

I was compelling the addicted character. So if I compel the consequence, give him a FP, he can turn down the compel by returning the FP? Right?
After that, the consequence is removed like any other? Or, being a vampire power, has to be removed by any other means?
About the first question, english is not my native so I apologize for it. Don`t mind it.

[Taran]

First question:

After that, the consequence is removed like any other? Or, being a vampire power, has to be removed by any other means?

This is considered a “consequential contest”
(see page 193); if you win, you inflict a relevant
consequence (usually Addicted) on the
victim, severity determined by the contest.

From my reading, it last as long as the consequence.  Depending on how many shifts you lose by that's the consequence you get:

the loser take a consequence
(page 203) in addition to his loss, depending on
how much he was beaten by in the contest: mild
for a two-shift loss, moderate for a four-shift
loss, and severe for a six-shift loss or greater
(round down in the case of in-between values).
If the group agrees, a loss of 8 shifts or more
could confer an extreme consequence, but it has
to be justified as per the usual rules (page 205).

So it lasts as long as a normal consequence: mild is until end of next scene; moderate until end of next session etc...

Next question:

I was compelling the addicted character. So if I compel the consequence, give him a FP, he can turn down the compel by returning the FP? Right?

Normally, when you compel, you offer a fp.  The player doesn't earn it until they accept the compel.  If they turn down the compel they LOSE a fp from their Own total.  So they'd be down 1 fp.

But Red Court Venom is different.  The vamp gets A FREE TAG EVERY SCENE.

Addicts are in pretty bad shape when
dealing with you—you don’t even need to
spend fate points to take advantage of this.
You get to tag (see page 106) their addiction
aspect every time you enter a new scene with
your new victim/pal, making it very easy to
gain—and keep—the upper hand.

So the vamp could compel you to let him feed on you again and again, every scene...or try to inflict new consequences etc...