If you are not an EU national, you will need a visa to enter the countries of study (France, Estonia, Belgium and Luxemboug). If you are concerned, once you have received your admission letter, we strongly advise you to apply at the earliest for Long-Stay Visa (Visa VLS-TS) at the French Consulate of your country of residence.
Your visa application must be carried out on France-Visas the official visa website for France. You will find the different steps you need to follow to complete your application here.
For a Long-Stay Visa it is recommended to submit your application between 2 to 3 months before arrival in France