Hi Ayazkhankakar,
This is the million dollar question but, unfortunately, there is no set way or procedure.
The truth is that, unless you're currently in Canada with work authorization, or you have some amazing connections in Canada, it is next to impossible for out-landers (people not living in Canada) who don't currently have work authorization, to get a job offer prior to applying for Express Entry. Work Authorization and Canadian Work Experience are very important to Canadian Employers.
And of course, it makes sense - why would they want to go through the trouble of hiring someone who is not yet in the country and who doesn't currently have work authorization, and have to go through all of the additional paperwork to sort this out (which may not even end up being approved by the government) when they have perfectly good candidates already on Canadian soil, with work authorization, that they can choose from instead.