You need to write that as an image into your SD card, so you need either a computer with an SD slot, or an external SD card reader. The Raspberry Pi homepage has very nice instructions on how to do it from several operating systems.
When done you can put that SD card into your Raspberry Pi 2 and power it on. Make sure to plug it also to an ethernet cable that’s connected to your router.
It will take a minute or two to boot. Once booted you’ll be able to login by connecting the raspi to a tv or monitor and a keyboard. Or, you can use ssh, but you’ll first need to know the IP address. To do that, try using the “webdm.local” address, like this:
If that doesn’t work, try installing the nmap package and searching your network for a host with ssh enabled:
Once you’ve found the address, you can ssh into it, using “ubuntu” as both the username and password: