There are lots of free templates that you can find online and here are a few websites where you can download them :
You can buy the carving kits from Supermarkets or online and they usually consist of a knife/saw, scoop and a poker for pricking holes through your template. There are also more advanced tools for some of the more complicated designs but for for the simpler designs you'll just need these 3 items.
First of all you need to slice the top of your pumpkin, it's easier to draw a line where you want it before cutting.
Then scoop out all of the seeds and some of the flesh, leaving the pumpkin around an inch thick - don't throw the seeds away as they can be roasted to make a snack.
Next you will need to choose a template - make sure you choose one that's not too large for your pumpkin - some of them show the best shape pumpkins for that template.
Using the poker punch holes around the edges of the parts that you need to cut out
Now it's time to carve the pieces out - careful if some of the lines are close together. You should be able to take the unwanted piece out or press it through into the pumpkin.
When all the pieces have been carved out place a tea light inside, light it, replace the lid and sit back and enjoy your handiwork before putting outside to impress your neighbours.