Interview's day ;)
Or you could say "Day of Interview" 

Hi everybody!
I am extremely nervous because my interview is at 5 o' clock in the afternoon. Could you give me some advices to do it well?

*The phrase "to do it well" sounds a little "off" or "awkward" for that sentence. You could end your sentence with "adivce" and you would still be perfectly understood. Or, instead of the awkward "to do it well" you coul say:
1) ..."so I can do well?"
2) ..."on how to do well?"
3) ..."for my interview to go well?"

How is going you day? 

How is your day going?

Interview day ;)  muchas veces cambiamos un substantivo (interview) a un adjectivo simplemente por poner la palabara antes de otra palabra (day).  es muy muy comun

Hi everybody!
I am extremely nervous because my interview is at 5 o' clock in the afternoon. Could you give me some advice about what I should say? about how I can do well? do it well?
How is your day going?