Tucking and breast forms (aka chicken fillets)
With regards to undergarments, there are many ways to “tuck”- you can wear tight spanx underwear or even make your own gaf, there are loads of tutorials for this on Youtube. There are also plenty of tutorials on how to create the illusion of a more feminine, curvaceous figure.
You can buy breast forms or chicken fillets to fill your bra, or simply just fill your bra with whatever you have to hand like a few pairs of tights.
You can also buy pads for your lower half too, to create the illusion of hips and bum. There are spanx underwear with pads already built in that you can buy online or you can even carve your own hip and bum pads the old fashioned way- from foam. There are Youtube tutorials about this too.
You can also create the illusion of a more feminine figure with styling techniques, for example a peplum dress will create the look of wider hips, but remember there are plenty of cisgender women who aren’t super curvy so when it comes to padding (and everything else outlined here) don’t forget it’s a personal choice, you do whatever you want; it’s your body!