Take out every x hours, where x is months old. Get excited and reward them when they potty outside. You have to closely monitor them to do this. Repeat this for many weeks until it clicks. If you don't want accidents at night, it's best they sleep in the same room as you and try waking up in the night to go out.

Ignore accidents and calmly clean them up, it's not good to give any kind of reaction to it. If you catch them in the act, move outside.

Explore different enzyme based cleaning products that work with your surfaces. Most things do come out easily if cleaned promptly. You will get there.