If your video card has a fan, you must make sure your power supply meets the video card maker's recommendation as you will have to plug a wire to power the fan
Now you must follow then insturctions provided with the video card as not all video cards are the same. Just remember, take your footwear off so you're in your socks. Touch a grounded peice of metal to preven pesky hardware frying.
To disable it, right click on the desktop, click properties ----> settings, then click 'advanced'. A new window will open. On the new window it should be set on the 'general' tab. You should click on the 'adapter' tab. It should state the basic info of your adapter. Click on properties again, you should see a an arrow at the bottom, click it, then click on 'disable', finally click ok. *NOTE, you may have to restart your PC.
Here is a screenshot to help with the coded text.