1984 Sinclair ZX Spectrum Unboxing and Connecting on LCD Tv

I was very lucky to have this almost new Spectrum ZX 48K from a very good friend as a gift.

The computer is in excellent condition and had inside the original power supply, warranty paper, receipt from 1984 and the cables needed for connecting it.

I am not sure if the keyboard is functioning properly because some of the buttons don't work.I haven't done any research yet how to use this little computer so if anyone can help will be appreciated.