press t till menu pops up
switch to Create tab
scroll down till you see Other: section then choose Armature (human in t pose golden icon)

in the lower right part of blender switch to object data tab (human in t pose silver icon)
under display check the X-ray to see bones even when they are inside objects

while in object mode select armature bone that we created earlier with right click
move it by pressing g to good place then rotate it with r
press tab to switch to edit mode

now you can choose either end of the bone and extend it by moving it with g

to make new bones just press the lover part of the bone (bigger triangle) and extrude

name bones properly so you know which one is which
you can do so by checking upper right part of blender and in the tree view expand Armature till you see bones
double click on the bone to rename it



set parents to the bones by going into the bone tab