What is a one-sentence summary of the following article?
If you plan to live stream voice, then a microphone is necessary. Most modern laptops have an internal microphone, but desktops will need to connect one externally. Streaming audio files or playlists can be done without an attached microphone. Enter your username and password and click "Log in". The main application window will load with 3 channels: Playlist, External Source, and Microphone. If you have a Facebook account, you can use it to sign in without creating a new account Dragging upwards will increase the channel volume, downwards will decrease. Dragging the slider all the way down will turn the channel off. Any combination of the 3 channels can be used simultaneously throughout a broadcast. You can also click a channel icon to quickly toggle a channel on and off. A monitor allows you to hear the sound that is playing through your stream. It is highly recommended to use headphones as a monitoring device if you plan to use a microphone during your stream. This button is in the bottom left corner of the window. A browse dialog will open to select sound and music files from your computer. Selected files will display in a list below your channels. You can add any number of files to a playlist. Drag and drop to rearrange tracks in the playlist. You can toggle the playlist display by clicking the "Show/Hide" button at the bottom of the Playlist channel. This button is at the bottom of the External Source channel and will open a menu displaying the available audio hardware you can use. Audio mixers or speakers are some examples of external sources that can be used. You can select "Reload devices" from the menu if you have a device connected but do not see it listed. This button will either be labeled "Select Source" or display the name or the microphone currently selected. The menu will display all microphones available for use. You can select "No Input" from the menu or turn the channel off if you do not want to use microphone input. This is indicated by the gear icon in the upper left corner of the window. Here you can enter a name/category for your stream, toggle recording, or test mode. A stream name/category will help other identify your stream on the mixlr website. All streams are recorded by default. You can toggle the feature by selecting the radio button. Test mode allows you to check sound levels and playback without streaming live. Close the Settings menu by clicking the gear icon a second time. This is the large button on the left side of the window. Audio from any of the 3 channels will begin broadcasting live to the Mixlr broadcast page. You can also start and stop streaming from the Settings menu. You can play, pause, skip, and repeat tracks in the playlist. If you have recording turned on, you will be prompted to listen to or save the recorded stream.

Summary:
Connect a microphone to your computer (optional). Download and open the Mixlr application. Sign in or create an account. Use the sliders to control the volume of each channel. Open the "Monitoring" menu and select a listening device. Click "Add Sounds" to add sound files to the playlist. Click "Select Source" to pull audio from other hardware connected to your computer. Select a microphone from the menu at the bottom of the Microphone channel. Open the "Settings" menu. Click the Mixlr icon to start your live stream. Use the playback controls to manipulate the playlist while you stream. Press "Stop" to stop the live stream.