You can buy from big stores floor leveller that is self levelling, I'm not sure what exactly you have already bought, but it sounds like it is a self levelling product.
Make sure your subfloor is screwed down tight and that there is no movement in it before you start.
You want to mix it up to a runny mixture about the consistancy of fondue chocolate, it MUST be mixed well and without lumps, so this usually requires a mixing tool attached to a drill for the quickest and easiest method.
Pour it onto the floor on either side of the raised section you spoke about and it will find a common level, you can help it out with a trowel if you feel the need.
As for laying the self stick tiles, first make sure you apply a "primer" to the floor it's available at any hardware store, it's usually white and a few bucks a bottle. To lay the tile first work out where all your lines will be and try to determine how the tiles will sit and what way looks best, lay out some of the tiles on the floor to get a better idea, once you have done that mark two sides of a central tile and useing a straight edge mark the two lines so that they are crossing over each other at 90 degrees, this will give you a place to start your first tile at the intersection of both lines.
The laying of the tiles is the easy part, once you lay the first one then the rest fall into place.