Booting right into KODI

Hello, first timer here.
I have a problem: When I power up my Raspberry Pi 2 it boots
right into KODI. And although I first had a linux O.S. distro installed (it is Raspbian I think but I forgot Sad)
I cannot see a method to get first boot into that distro and then choose KODI.
How can I solve this?
Thanks.