Is that f(x) = -√(x - 1) ?

I'm assuming by your spacing, you meant f(x) = -√(x - 1).

Set y = f(x).

Pick some values of x. Compute y.

Graph the points.

If x = 1, y = 0, giving the point (1, 0).

If x = 2, y = -1, giving the point (2, -1).

If x = 5, y = -2, giving the point (5, -2).

etc.

Plot the points and draw the curve through them.