First, you create an armature system, then you make sure to name all the bones. Then, create a bunch of vertex groups that have names corresponding to the bone that will control them, then assign the verticies that are going to be controlled to their vertex group, and then assign the armature to the mesh using the modifiers menu in the mesh, and make sure to select the vertex groups button.
As a practical example, you create an armature named "Man Armature" and the bone on that armature that you want to control the left foot you name "Left Foot" and on the mesh you create a vertex group named "Left Foot" and you select all the vertexes in the left foot of the mesh and assign them to the vertex group "Left Foot." Then you go to modifiers and select the modifier option "armature" from the drop-down menu and type "Man Armature into the armature name field and select the vertex group deform button.