Please my 2004 rx8 wont start

So I was driving my rx8 last week maybe 5 min before getting home my radio started making noises and the windows stopped workin; the next day I tried turning my car on nothing happened. the car woulnt start over. at first though it was the battery so I tried jumper cables, still nothing. I check the fuses everything seems ok but the ST relay on one of the sides the relay doesn't have power at all. it seems that I need anew battery for sure because when I put the jumper cables to put power on my car then I put a end of a wire inside where the ST relay goes and the other end I put it to the power screw at the end of the fuse box. the car starter regular( I had the key open) remember I had the jumper cables on. I left it there for no more than 10 min and the battery drained. so I neen a battery I believe but I have a back ground problem but I don't know where the ST relay wires go to or what else they control . I don't if I explain myself . thanks for reading and trying to help