Burn it to a DVD and use a DVD drive if you have one, if not they're like $25 these days; external USB ones can be had for under $100 in many places (around here).
Or
If it was downloaded as an ISO you should be able to use Microsoft's Windows 7 USB/DVD Download Tool to install via a USB flash drive.
The link is a little hard to find on the page but it's there. If you Google "Windows 7 USB/DVD Download Tool" there's a couple other download sources (like cnet.com).