Reliance Retail

I sometime wonder how big companies like tata, reliance, sahara, wipro, infosys etc take employees, i seldom see ads in paper and if they appear total positions that are on offer remain 10-15.I dont know from where papers publish wipro to take 20000 employee shara has 9 lac workers or field force, reliance is opening over 2000 retail outlets. i am sure for these 100000 of retail outlets manpoer would be needed. from where i can get a chance.i am a civil engineer and want to work with sahara for its sahara city home project. i would be happy if i get a chance with reliance of dlf etc.