  In this paper, we investigate the existence of nonnegative solutions for the
problem $$ -\mathcal{L}_{K}u+V(x)u=f(u) $$ in $\mathbb R^n$, where
$-\mathcal{L}_{K}$ is a integro-differential operator with measurable kernel
$K$ and $V$ is a continuous potential. Under apropriate hypothesis, we prove,
using variational methods, that the above equation has solution.
