How to upload a CSV file in dashlet?

Hello. I want to mass - upload some date into one of our modules. For that I made a dashlet, that has a file input type and a button. I am having trouble upload the file from the input towards a custom REST api. Basically I do not know how to start. I have a function in the JS controller that is correctly called upon button click but.. how to upload in sugar's version of JQUERY?