How to connect windows 8 HP laptop to Toshiba TV using HDMI

HI
I really need someone to help me, its been months and I cant figure it out...

I connected my laptop to my Toshiba TV, the screen from my computer displayed on my TV. Great it worked but the sound on the TV isn't working at all and no sound on computer. When I tried to play a video on my laptop to display on the TV that I downloaded the sound on the TV didn't work or on the computer. It keeps saying on my laptop screen resolution is low, what does that mean?

what am I do wrong, please someone help me, I would like to watch my movies from my computer onto my Toshiba TV.