Q: bootcamp removed mac and windows 10 installed

hi! i am using macBook pro i was installing windows 10 on my bootcamp but by mistake my mac had been removed and window installed i am helpless how to boot mac again because there is no solution online also i have downloade OSX lion.... problem is not that much my half space which was alloted to mac, that  2 drives i can see but i cant use those partitions please help me how to make a bootable pen drive of osx lion and how to install it too....
right now only windows is working with half space