You have to shake it the injectable soulution up when it separates. The reason it separates is because it is a water based solution.
MK & snipe are right. Anavar is a better option unless you are bent on using injectables and Winstrol is no good for your joints. Anavar is actually one of the safest AAS you can use.
But if you do choose to use the winstrol over the anavar, the injectable is better. You will see more strength gains for sure. But be aware of its half-life because you will have to inject often.