How to receive data from SQLServer

i have a powerfull server , now i installed Microsoft SQLServer on My Server , however , i want to receive data from my SQLServer like online program, What is next my step? Would i change the ConnectingString and this will be ok? or it need more something ? if it is, tell me Youtube links or some answers with description . someone tell me the best way is making "API" , would someone tell me whats the best start step ? You Know ? this program is working on local database , i want to make that online and i need some description to start. if there is any way with API and ConnectingString or something , just tell the key word with some description , or links , videos...

my program developed by C# .

i can also use MYsql . but my best choice is MSserver for now.

thaks for help .