Finding Equation of Motion Using Scalar Field Lagrangian

Homework Statement

I must find the following equation of motion:

φ'' + 3Hφ' + dV/dφ = 0

Using the scalar field Lagrangian:

(replace the -1/2m^2φ^2 term with a generic V(φ) term though)

with the Euler-Lagrange Equation

I know that I must assume φ = φ(t) and the scale factor a = a(t)