Wirms tend to create colonies in areas where humans do not often go, and near things such as trees or rock formations, which help in hiding their colonies. They prefer areas with plentiful resources and stable ground, although there are colonies that can be found in less desirable conditions. 

Finding a place where wirms live isn't very hard by itself, as they inhabit nearly every place on Earth, but what happens after you stumble upon a colony depends on whether or not the wirms there perceive you as a threat. Often, if a human is just seen near a colony, the wirms that live there will go into hiding. If the human spotted seems threatening however, the wirms will start to become more aggressive, and may start to attack.

In order to signal that you are not a threat, it is advised that:

• You go looking for them in groups of less than three.
• You wear muted colors. Congratulations! You have found one of my secrets. Here is your reward

It is advised that you carry dried fruit in case you the situation escalates. If it does get to the point where you need it, you should locate a nearby rock and place a few pieces of the fruit on that rock. Shiny objects will also often work for this purpose, although those are less recommended because of the difficulty in dividing them. You will most likely not see exactly when the wirms take the fruit or object, but if they do take it, then you should be free to leave the area. If the situation starts escalating and you successfully de-escalate it, the wirms in that colony will be more inclined to trust you in the future, and you might want to try going back to that area at a later date.

Wirm colonies are very well hidden, so unless you know the small signs that there is a colony, you will likely not know that a colony is nearby unless the wirms inhabiting it decide to make themselves known. 

Besides all of this, another way to meet a wirm is for me to give you a tiny wirm. Go here to learn more about that.