What kind of HPLC system are you using? Do you have software for data analysis? Oftentimes your software will calculate peak areas for your samples and standards and calculate your sample concentrations too.
Relationship between area and concentration is usually linear over some concentration range. If your peaks are well shaped, you can measure peak heights instead of areas (If you're doing without software, this is an attractive option)
Do you have a protocol for what you're doing? Columnn manufacturers often have a variety of protocols available and their websites often provide basic information on HPLC. Try Waters, Varian, Alltech, Hamilton