Hi jasim.hd,

This is a good question. You want to hit the strings with the tips of your finger, it doesn't have to be super exact or precise but you want your fingers to be as straight onto the fretboard as possible. The more of your fingertip you use, the better.

Lisa talks about this exact topic here:

https://www.guitartricks.com/lesson.php?input=22138&s_id=1777