How do I make my electrical enclosure waterproof, what type of connectors I use?
Nothing is water proof, not even submarines (sometimes) unless you go for a fully hermetically sealed design and this doesn't sound like an option to me so, you have to design to meet a certain IP rating (where IP stands for "ingress protection"). This is used in the EU but Nema (see below) is used in North America: -



Then you have to choose appropriate cable glands for incoming cables. They have to have the appropriate ratings too. 



You also have to consider the temperature range that the box may be subject to and analyse how much humidity can be present. Water will get in no matter how hard you try and stop it and humidity/temperature changes are quite challenging. In the end a lot of designs use a drain plug to allow water that has entered by osmosis or capillary action to drain away harmlessly.

If you are in the US this comparison chart may be useful: -