I have a new MacBook Pro which has Windows 7 installed so I have only ever used it as a PC, I would like to use the apple system but was never shown how to do this and I cannot even work out how to switch it on . If I just press power iI get windows7

I switch the power on on my MacBook Pro I get windows7

this is no problem but I love my IPad and would like to use the apple system on my MacBook .

CAn anyone tell me which keys I press to change from windows 7 to Apple most articles I have read tell you it is easy but not one says "firstly press x then press y and when you see c press v so I no idea how to do it,

I am well educated but I am 75 so I do not understand the jargon but I am fairly good at using computers and I do like the app system.

I Would be very pleased if someone can advise me

best regards

TOm