You highlight the first line in your browser, go to the edit menu and select copy. Then, you open a terminal, and paste it in using the edit menu > paste command. Then you press they enter key. Repeat the proces for the second line:
sudo cp -r $HOME/Desktop/SlicknesS-black /usr/share/themes <enter>
sudo chmod 777 /usr/share/themes/SlicknesS-black/Slickness-black.jpg <enter>
Also, if you can edit your LQ profile to include which distribution you're using, it'll make helping you with specific problems much easier.