Since you post this under skilled worker, I assume you want to apply as a skilled worker. You would need an employer to give you a job offer but first it has to go through Service Canada. The generally call this AEO (Arranged Employment Offer). You can read about them at http://www.hrsdc.gc.ca/eng/workplaceskills/foreign_workers/supperimm.shtml Once you have the AEO, you can use it to apply as a skilled worker as long as you have at least 67 points on the self-assessment, see http://www.cic.gc.ca/english/immigrate/skilled/assess/index.asp
There are other ways to get sponsored by an employer, for example through a provincial nominee program, see http://www.cic.gc.ca/english/immigrate/provincial/index.asp
