How do I replace and install a new keyboard?

First of all, we better be talking about a desktop, the keyboard replaces itself. If the laptop needs a new keyboard, it might be time to replace the laptop.

laptop keyboard can be replaced, but some models are easier and cheaper to replace than others. the keyboard in the Dell Inspiron 1545 is one of the easiest to replace, hands down First, you need to purchase a replacement keyboard.

The best way, so that nothing else gets broken in the process, is to let someone else do it. Go only to your laptop's brand's authorized service center. If you don't know where, look in the manual, the brand's official website or ask the store you bought it from.

PC tends to be buy a new keyboard of choice and connect via USB, laptop would be more complicated.

You have posted this in the laptop section - if it is a PC then PC keyboards are just plug and play, so I assume you are wanting to replace a laptop keyboard.

To be honest if you have to ask the question then I would recommend you take the laptop to a workshop and let them do it. Some laptops are relatively easy to swap out the keyboard, others are more complicated, and you risk damaging many of the internal delicate cables and connectors  if you don't know what you are doing. You also have the problem of sourcing a new keyboard, laptop keyboards are not generic unlike PCs keyboards so they can't be bought off the shelf as manufacturers only sell spares to the trade and repair shops, not to the end user

As you haven't provided any details then that's the best advice I can give. This is not me being rude just saying how I see it

First Shut Down the Computer, Then Just Insert Your New Keyboard into USB Port. Now Start your PC, Windows OS System Automatically install Your keyboard. Thats Ok

The repair by replacement of a keyboard is not easy.  I have done it on an HP Elitebook.  Also I took apart a Lenovo laptop to swap motherboard.

How to do yours depends on brand and model of the laptop.  See any Youtube videos how to.  There might be a service manual on line with pictures and instructions.

You might try an external keyboard.  Most USB models should work straight away after plugging in.

most are plug n play.

For a tower? unplug the old keyboard, plug in the new one. probably don't even have to turn the computer off. for a laptop its a similar process but you will need a compatible keyboard and tools enough to open and close back up your laptop.