What part of the waveform do I start on?

[Dimensions]

Okay so I know this is a super basic question, but I want to make sure I've been doing this right...

The first image is the sound totally zoomed out
The second is a bit more zoomed in, so you can see that I need to fill in that gap
The third and fourth is the same as the second except... I maxed the volume so that the waveform is more visible. Firstly... Is this a good technique to make sure I am perfectly aligned? Secondly, the 3rd has a purple curser where the waveform gets really loud (transient?), and the 4th is before: DO I SET THE BEGINNING OF THE WAVEFORM ON THE TRANSIENT, OR BEFORE?

Also is there a video you can recommend that explains this?

Thank you!

[carrieres]

on the third image there is a pink line, i would start from here by right clicking and place a marker, it is right on a zero crossing point.