it's a good use of the word.
But the tense is wrong. You are talking about something you are doing now, but telling a third person. This suggests that you are not 'venting' now. It's confusing.
Here are the ways you could use Vent. Think of it as a synonym for 'let off steam' or 'explain your anger / frustration so that you feel better'
'I just need to vent'
'I vented to my friend'
'i had a really good vent and now I feel better'
'do you mind if I vent?'
'[some angry talk about third person] (calms down) I apologize, I am just venting'
You don't really need to say what you are venting, but if you do, use a word like anger, or frustration - an emotion that is charged with energy.