U shd start trying as Long as u intend to get pregnant because it's better to have 'fresh' sperm so u need to try a few times instead of waiting till u have ovulated which might be a little too late
Towards your right side I can see slightly darker lines so when the top part turns dark pink means ovulation date. You can try 2-3 days until ovulation date.
Only the last 2 or 3 is positive test.