Often combined in a single tablet with 100mg of Sildenafil.
Take 1 hour before if possible. The Sildenafil kicks in before the Dapoxetine reaches peak absorption.
Double-blind cross over with placebo confirms a significant effect (~2x duration). You may find you cannot ejaculate at all at that dose, and end up taking half a pill.
Or you take the full dose on occasion and go for as long as your partner desires.