Did they ever explain how Apes got into wrecked spaceship????

In the previous film Beneath Planet of the Apes...Brent and co. enter the scene in what was clearly a wrecked space ship "computers trashed" and fuselage in pieces....


Taylor hits the Doomsday button and you get the cheesy monologue.....supposedly Apes are on their way Superman-style through time warp back in time????

Is that pretty much it?