here is how
Click the Dash -> type Terminal

open up the terminal

then type cd PATH_TO_THE_FOLDER_CONTAINING_THE_DEBS

then run

sudo dpkg -i *.deb

basically, what this does is fills in the rest of the name in place of the * character. You may encounter an error saying dependencies not met, if you see this then you can run

sudo apt-get install -f

This usually will cause apt to download the missing dependencies.