Just graph the function up to and/or including the points indicated.
- if you have a piecewise function defined as y=x when x < 0
y=-x when x >=1
You would graph y=x from the negative direction up to 0 (but leaving an open circle on 0 because the function is not defined there
Then start at point 1 (this time with a closed circle because y=-x is defined at 1, and graph y=-x.