If your Mac constantly tries to join a network for which your credentials have expired, or a network that has a weaker signal than the others around it, you may want to remove it from your profile. If you follow this path, enter your credentials and click 'Join,' and the network will be added to your profile. Once you have completed these tasks, you can click 'OK.' However, if you think the network may be listed, you can also try to click 'Show Networks' and select it from a window that will appear. A window will then pop up prompting you to enter the name of the network manually, and to select its security type from a drop-down menu option. To add a network, click the plus symbol (+) under the list of preferred networks. This is the window through which you'll be able to add or remove a network, or reorder your network preferences. Once these steps have been completed, click on the 'Advanced.' button on the bottom right of the window. Make sure you have 'Wi-Fi' selected on the left-hand side, and that the status bar says 'Connected.' From there, click on the 'Network' option toward the middle of the screen. To begin, go to your Dock and click on 'System Preferences,' the silver app icon that looks like a set of gears.
Note: For this article, I am using a 2016 MacBook Pro with Touch Bar, running macOS Sierra, but these steps should work for a few prior operating systems as well.
