Should I keep my grow light in before the seedlings pop out? And at what time should I start a light schedule?
Yes you can put light on them as soon as they are planted and a good starting out schedule is 18/6. What stating and what type of seeds are they?
Sour diesel and blueberry so even before they pop I should be turning the
light off for 6 hours a day?
I have them under light as soon as I plant mine. I use 18/6 up until flower then I got to 12/12.
I usually put my lights on also once I put the seed in the ground. That way when it pops up it will have light. As @Hawkeye_diesel stated 18/6 is a good light schedule. (That would be 18 hours on/ 6 hours off) you will use this light schedule throughout the entire Veg cycle.