We suggest you have a basic understanding of English before using the trainers, and here's why:
Each trainer comes with two types of minimal pairs. For example, with a Russian trainer, you get Russian-Russian (which will be valuable to anyone studying Russian) and English-Russian (which are optimized for English speakers.) The English-Russian pairs may be frustrating for someone who does not speak any English just because of the added difficulty level of being asked to differentiate between two unfamiliar sounds.
The trainers also come with English instructional videos on how pronunciation works, which may also hinder learning if you're unable to understand it. This doesn't mean you need to be a native English speaker - just that the more comfortable you are with English, the more you will get out using the trainers.