x^2+y^2+z-1=0

Now x^2+y^2-1=-z

and z=1-(x^2+y^2)

Do you know what is z1=x^2+y^2. It is paraboloid.

Its sections x^2+y^2=k or x^2+y^2=Sqrt[k]^2 are circles with radius Sqrt[k].

So first draw the paraboloid. Then reflect it around the z-axis (just turn it upside down), and finally move it for 1 unit up in the z-axis.

Regards.

P.S The graph that you need will look something like this: