Switch to dd-wrt
Download the following firmware here. Save this somewhere handy (like your Desktop). NOTE: This firmware will change you from stock Netgear firmware to dd-wrt. You'll still want to get a newer version of dd-wrt to run on. More on that shortly.
Go to the R7500v2's web configuration page (stock firmware can get you there by going to or assuming defaults)
Click on the Advanced tab
Go to Administration > Firmware Upgrade
Click the Browse button and navigate to where you downloaded R7500v2-factory-to-ddwrt.img and select OK (or whatever your browser uses for selection).
Click Upload. After this completes after 2-3 minutes, your R7500v2 will reboot and you will be on an initial version of dd-wrt. Welcome! But wait, there's more...
Go to your dd-wrt configuration screen (again, that's going to be NOTE: if your stock firmware was configured for a different subnet than the default, you may have to change your computer's IP address accordingly. No, this tutorial isn't that thorough.
You will need to select an initial username and password. You can do the whole 'admin'/'password' thing like Netgear or you can not be a chump and do something half-way secure. Your call.
Before configuring anything else, you'll want to get a stable, more recent build of dd-wrt for your R7500v2. There are a few good places but I always recommend myopenrouter.com for people new to open source firmware using Netgear hardware. As of this post, this is the version I'm using: DD-WRT Kong Mod for NETGEAR R7500v2 (2018-02-15)(BIN). Download the file there or myopenrouter.com (registration required) and again, put it in a handy location.
Same as before, you flash the router in the web configuration page:
Click on the Administration tab
Click on the Firmware Upgrade sub-tab
Click Choose File and navigate to your new firmware version (if you chose my version, the file is named ddwrt-netgear-R7500v2.bin or it's ddwrt-netgear-R7500v2_2018-2-15.bin if you got it from myopenrouter.com).
Click on the blue Upgrade button at the bottom and follow the prompts.
After the upgrade is complete, now is the time to start setting up your router, configure your wireless network, etc. There are other tutorials for that.
Hopefully that helps you get to dd-wrt quickly and safely. There's a way to revert, too, if you don't like it but we'll leave that for another tutorial, too.