My daughter was showing signs of interest at about 17 months too. We just went on the potty occasionally, whenever she asked. I also watched for her signs that she had to poop and we would sit on the potty then. It ended up, she was pooping in the potty almost exclusively from 19 months on. I didn't put her in underwear until she was 2. Here is what I did after they turned 2.
I have a son (8 yrs) & two daughters (5 1/2 & 2) I just finished potty training my 2 year old last month. I watched for the morning that my kids woke up dry in the morning. That was the day we started potty training. Then you know they have the muscle control to hold it for a longer period of time. I then went cold turkey, no pull ups no diapers, just underwear, even at night. Make sure you have about a week where you don't have much running around to do & can basically stay put in the house. Put her on a schedule where you put her on to "try" every 30 minutes or so. You have to stay right by her side, so if she has an accident you can tell her to stop & run her to the potty. She has to have accidents to realize that from now on peeing in her pants equals being all wet. ( Also, you have to be unhappy about accidents, not mad, but it is not OK. Let her see you are disappointed.) Going back & forth between underwear & pull ups confuses them. Sometimes they pee in their pants and are dry & sometimes they are wet. Too confusing. They only go in the potty from now on. Period. (You have to be ready to lay down the law & not waffle) Even wetting the bed a few times helps to trigger the part of the brain that wakes us all up when we have to go in the night. I'm telling you, from 3 times of successful training, this approach takes one week (there will be accidents and you will feel like pulling your hair out mid-week) to be fully trained day, night & naps. No turning back. My friends who separate training during the day and night, end up struggling for months, sometimes years to get the nighttime diaper off. They will get it much quicker if you go cold turkey. After the week is over & we are ready to venture out into the world I put her on the potty before we leave and anytime before we get back in the car. I keep one of those waterproof pads in the car seat and I have a waterproof bag that I carry her potty seat (that fits on any toilet), clorox wipes, a change of clothes & underwear, & a ziploc for any wet clothes. At the end of the week she was telling me when she had to go. As for nighttime, I limit her drinks for about an hour before bed, put her on before bed and then put her on the potty again before I go to bed (about 3 hours after she went to bed). Then she can hold it until morning.
Hope that helps! Good luck & have confidence in her! She can do it!