This QuickStart will help you through the initial set up of your Raspberry PI 3. After getting it set up, take a look at our other QuickStarts that will help you do things like configure the Raspberry PI 3 to use the Audio Jack rather than HDMI for audio, Set up Remote Desktop, Enable Bluetooth and pair with a Bluetooth Headset and more.
The Raspberry PI 3 comes with a good set of instructions to get you started however, the first struggle I had and from Googling others have as well is getting the "Demonic" plug removed from the Power Adapter and your proper plug attached. It is actually quite simple once someone points it out. In the center of the plug is a T shape. Press on that and slide. Now slide the proper one on until it clicks.
Before plugging in, make sure the MicroSD card is inserted. It should go in easy, if not then you have it upside down. Once you have it in, you can put the Raspberry PI in its inclosure with the SD card down first. If you do this it should slip into the case easily. Next make sure all your peripherals such as USB keyboard, USB mouse, speakers, microphones, HDMI cable are all plugged in then plug in the power.
Once you power on it will automatically detect the keyboard and mouse and start the set up of the Raspberry OS. The wizard is pretty straight forward getting you set up.
If you run into problems getting your Raspberry PI 3 set up or if you have other questions, let me know. My email address is firstname.lastname@example.org. Please follow me on twitter at @BerryPIChris