After successful method development of your compound of interest, you need to make dilutions of calibration standards to generate regression equation/calibration curve. Then by using the regression equation, you can quantify the amount of analyte by peak area.
You can have a look at: https://www.ema.europa.eu/en/documents/scientific-guideline/ich-q-2-r1-validation-analytical-procedures-text-methodology-step-5_en.pdf