Hello & welcome to the Seamly2D forum, @annesophiev
Up until now, you seem to have been using the Draping Method of flat pattern making, which is quite different to how Seamly2D works, which is using measurements to create points at certain distances from a point of origin to get a ‘Basic’ Sloper on which one would move things & add others to create a pattern which one could resize according to the measurements attached to the file.
The ‘easy’ way to get started with Seamly2D, would be to find one of many basic bodice patterns and a measurement file that is already posted with it (or you could download one from the my pattern cloud) and use it to practice on until you become familiar with moving and adding points to create the designs that you already have.
The ‘hard’ way would be to find a book that will help you to create your own basic sloper and also teach you how to change things to create the pattern that you envisage.
With the ‘hard’ way, you will have a better basic understanding of the why’s and wherefore’s you need to do things in a certain way and how to reference the measurements to get the size correct. I sincerely recommend this way.
A picture is flat and doesn’t reference the measurements needed to resize a pattern. You could measure each area and copy the pattern into Seamly2D directly, and it would work, but I’d suggest first learning how the program works before attempting this.