Summarize:

Go to Settings in menu bar at the top of the screen and choose the Broadcast Settings tab. Change the mode drop-down option to "File output only," and then set the directory box that will appear under it to the location you want to save the video. This is where your recorded files will be saved each time you end a recording. Head back to the main screen of OBS, right-click the "Sources" list box at the bottom of the screen, scroll over "Add," and select what source you would like to record from. To record World of Warcraft, there are a few options available: Window CaptureThis is useful if you are playing the game in windowed mode. Monitor CaptureThis mode will capture everything happening on your screen whilst recording. Video Capture DeviceA common component of gameplay videos involving a picture-in-picture display showing the player's actions and expressions alongside the game they are playing. This mode will not record the game itself but will record the player using a webcam, which can add a personalized touch to a video. If you choose to use this option, you will have to add another source to simultaneously record the game. Game CaptureThis will record only what happens in the game, even if the game is minimized on your computer. Depending on which source you chose, a menu will come up containing a few settings specific to that source. These can be left at default unless you want to hide your mouse by clicking the check box at the top of the menu or change the brightness in the video using the slider in the center of the menu. Click "OK" in the bottom right after reviewing these settings. Recording video is a memory-consuming task for a computer. If you do not have a machine capable of recording and processing graphics at the same time, then it is recommended to turn your game settings down to accommodate the memory being used to record video. If your computer is capable of recording and processing graphics at the same time, you may skip this as well as the next step; however, skipping these two steps is not recommended. Be sure to shut down any unnecessary programs to free up as much memory as possible. This will ensure that the game will run smoothly and produce a high-quality video.
Set the saved file path. Choose what source you will record from. Review some specific settings. Change your World of Warcraft settings based on your computer's capabilities. Shut down any unnecessary programs.