where I am now is
$\displaystyle
4\int \frac{sin^2\theta}{cos^3\theta} d\theta
$
how do I complete this?
You have $\displaystyle 4\int \frac{\sin^2\theta}{(1 - \sin^2 \theta) \cos \theta} \, d\theta$. Now make the substitution $\displaystyle u = \sin \theta$.