Place it over or in soil and watch it root. It looks like some sort of opuntia (perhaps O. cylindrica) and in nature, this is one of the primary ways opuntia reproduces - by having segments knocked onto the ground by animals, wind, rain etc. If you lay it on its side, it'll root where the segment touches moist soil. you can also stick it INTO soil (vertically) and it should root that way also.

Thank you very much Josue for fast reply, I will try this immediately!

Make sure it is not kept wet or it may rot. Use fast draining mix, preferably without peat.

Thanks for your advice too, Rina :)