Put her on the toilet with her nappy on. Then slowly move away from that.
We started 2 weeks ago, we have a potty upstairs and downstairs and spent a few days at home in dresses and pants so it was easy to pull them down quickly. Before we started we had been reading a book 'Elodie says goodbye to nappies'. Every time she sat on the potty to try and wee we made a big fuss and gave her a high 5. Then at the first sign of her going to the toilet we put her on the potty and celebrated what did go in with a sticker on her chart. We had a couple of accidents the first 2 days and nothing since then. We didn't make a big deal out of accidents and really made a fuss of celebrating each time she went on the potty. We have a travel potty too which has been great for quick access when we are out. She has also loved having bluey and princess pants we got from asda and picking which ones she will wear 😂
We've just started, but in terms of my little one she was asking to use the potty for wees and using it successfully prior to us starting so she had the idea of how to let go. We're using the method in the oh crap book. If you can get her to sit on the toilet it might be worth getting a stool so her feet are supported and have a cup with a straw in it and encourage her to blow bubbles in it as it can help relax pelvic floor