right now i am entering future finish and start dates by entering into baseline start and finsih dates column. because someone gave me those dates which are all in next year. BUT it doesnt calculate the baseline duration column or duration column automatically when i enter those dates. how can i make it calculate the durations?

or am i approaching this wrong way and i should first enter a start activity, enter its start date and duration, and then its finish date will be calculated automatically and then all other activiteis will be following that and i just enter their durations and they will be calculated automatically?