If messing around with your router settings seems too daunting, and you have a few dollars to spare, invest in a Wi-Fi extender or repeater. These devices plug into a spare wall socket, connect to the wireless internet getting beamed out by your router, and extend it.
They're (usually) simple to set up, easy to use, and can instantly get rid of Wi-Fi dead zones in your house. The extended or repeated wireless signals won't be as strong as the ones coming straight from your router, so, again, positioning is important. Try to use these devices to connect gadgets that don't need a huge amount of bandwidth.
You've got plenty of options: Take a look at the Linksys AC1900 ($80, Amazon) or the Netgear EX7300 ($100, Amazon). Make sure the maximum supported Wi-Fi standard (e.g., 802.11ac) matches that of your router so you get as speedy a connection as possible.