Astral projection with lights on

I was reading the blog and it shows a method for soul travel by looking at the line between the ceiling and wall, I was wondering if it is okay to astral project/soul travel whilst electric light is on.

It is perfectly ok. A lot of projectors prefer to travel during the day, as the world is much more illuminated.

What would be the method for exiting though?

What do you mean? Whichever exit method you would use at night, light shouldn’t make much difference. If you haven’t learned any methods, I would check out Robert Bruce’s Astral Dynamics, preferably the revised edition. Should be able to get a used copy pretty cheap online.