Im trying to install unbuntu 18 unto my ibm windows 8 need help

I Have an IBM (dell Laptop) with windows 8 i am trying to get ubuntu 18 or whatever works best on the computer too, ive downloaded the ubuntu 18 and another file that is supposed to make it work and setup a dual drive or spkit partition (whatever its called). Just need some help, It says something about the ISO file which i see in the directory i.e ubuntu.iso when i do a search in dos windows cmd prompt,, just at a loss with this type of system, Ive used oniux before but have never set it up from scratch.. my sone has dont it for me before.. signed Preplexed