How long i have to charge battery for the first time?

[AC Question]

I have samsung galaxy s6 edge plus

 

[belodion]

Welcome.

I don't think there's any 'have to' about it. I charge to 100% then keep the charger connected for twenty minutes or so beyond that, but others would do it differently. I doubt that it matters very much.
Check this for more info about batteries:
http://forums.androidcentral.com/showthread.php?t=500054