Transfer to your jar, add the caraway seeds if using, and tamp down with the end of a rolling pin. When the cabbage is compressed and submerged place the sandwich bag filled with marbles to keep it from floating.
Do not close the lid. Instead, place a clean tea towel over the neck of the jar and tie with string or an elastic band. This keeps bugs out but allows air to flow which is necessary in the fermentation process.

Finally store in a cool, dark, place for 28 days. It's perfectly good to eat at any time, but I find 28 days is best. Check every 3 to 4 days, scraping away any mold, and tamping down again.
The mold actually develops from the same kind of bacteria that exists in yoghurt, and is harmless. Some people don't like eating moldy food though.

After 28 days put the lid on and refrigerate. If your brine stops covering your 'kraut, dissolve 1 teaspoon of salt in 1 cup of water and top up.