Use the mouse and left mouse button to guess letters to solve the puzzle.
Words is about as basic as a game can get, but the ability to choose the level of difficulty you want makes it one of the best word games online. The game itself is fairly graphics intensive so if you computer had a hard time handling this sort of game, choose a lower graphics quality setting. The game will still look great but you won't have to worry about lagging.
The premise behind Words is simple. You are given a puzzle much like you would given in hangman with a clue at the top of the screen that tells you category the puzzle falls under. As far as the controls go, they're pretty standard when it comes to online word games. Click on the letters you want to guess. If you guess right, the letter will appear in the puzzle and a check mark will appear over the letter. If you guess wrong, an 'x' will appear over the letter. When you've filled in all of the letters correctly, you move on to the next level. If you run out of guesses or run out of time your game is over.
Words offers a variety of categories but you'll need to have a fair bit of pop-culture knowledge to do well. With categories like, 'actor/actress', 'movie title', 'football player/club', the game is much more challenging if you don't know some of the more popular names and titles. The great thing about this game that many other words games online don't offer is the ability to customize how many guesses you have (turns) and how fast the timer runs. If you're having trouble getting the puzzles because you aren't familiar with the categories, try giving yourself a bit more time or a few extra guesses. This can make the game a bit too easy for those who are looking for a real challenge, but it can make the game a little less impossible if you don't know your pop-culture figures.
Overall, Words is a great game to kill a little time with but it may not provide the challenge more experience word game players are looking for. To up the challenge choose the lowest number of guesses available and give yourself the least time possible. This will make the game much harder and give you the challenge you're looking for.