That is up to you. I take mine in the am with breakfast. If it makes you drowsy you can take it at bedtime. This drug can cause insomnia so you might want to try the am first until you know how it affects you.
Sertraline can be taken in either the am or pm. Since two of its POSSIBLE side effects are insomnia and fatigue..............and I am NOT saying you will experience either one of those, it's really up to you to just try it and see how it affects you. If you do experience insomnia, then take it in the am. If there is no insomnia, but you find it makes you tired, taking it at night would be the better choice. Both of these side effects, IF you even experience them, should pass within a week or two as your body adjusts. If they don't, let your doctor know.
Actually your doctor DID tell you when to take them............once a day. The choice is yours.
I hope you have better luck with the Zoloft than you did with the mirtazapine.
RubyWitch