FYI - There’s a toggle switch on the sell order after you enter your data (stock, limit price, etc.). Says “After hours trading turned (on/off)”. Slide it to the right and it turns green. Pretty impressed as I had read you need to call and talk with them directly before they’d authorize after hours trading. No problem. Thought others might find it useful. Not all stocks trade after hours. In my case a day-only limit sell order missed the mark (too high) by a few cents today. So I decided to re-submit & keep it open through the evening. Not sure. But I think the after-hours trading ends at 8:00 PM.
Likely, you will need to have previously acknowledged when prompted that you are a “highly experienced” investor. Heck, even buying conservative funds like GATEX require that requisite because they deal in options. Likely, too, you won’t see the option displayed during regular trading hours.