I made a new airline, how I can buy planes?
As a new airline you should not BUY planes but LEASE them instead.
Go to Management / Aircraft Manufacturers and meet your choice - in case you like toi lease new planes OR
go to Management / Aircraft Market and meet your choice there - in case you like to lease used planes.
.... an read this first
http://community.airlinesim.aero/topic/8123-as-for-beginners-an-attempted-blog/