С помощью вспомогательного глагола TO BE. Глагол to be имеет 3 формы - am, is, are. А в конце смыслового глагола добавляем частичку ing.
Example Present Simple - I go to school
Present Continuous - I am going to school
Pres. Simp. He eats biscuits.
Pres. Cont. - He is eating biscuits.
Pres Simp.- We drink coffee
Pres Cont. - We are drinking coffee