Everything Owlman had learned about this world thus far led him to the conclusion that the epicenter of weirdness, metahuman activity, and super-science was a place called S.T.A.R. Labs. There was one on Earth 27, too, but it had been decommissioned and then converted into a fortress by Johnny Quick.
On Earth 1, S.T.A.R. Labs served as the base for the Flash.
Fine. That was where he would start, then.