You don't. Only a small number of verbs show a difference between Present Simple and Present Continous. For example "chodzić" (to go, to walk) vs "iść" (to be going, to be walking) or "nieść" (to be carrying) vs "nosić" (to carry and also to wear).
Dziękuję bardzo Marek! Now I got the solution for a personal mystery - why'niisie' was market wrong when translated to 'carry' but not when translated to 'carrying'. You made my day - virtual lingot to you from Sweden!