Some sites allow applicants to post their resume to be viewed by prospective employers.
Register with a handful of sites. This will give you access to more employers and opportunities. Try to look for sites that post jobs similar to the ones you would apply for. Most databases will allow you to search by job category, location, keyword, permanent vs. temporary, part-time vs. full time, etc. Some seekers start with a very narrow search and expand their options as necessary while others prefer to conduct a very broad search and scroll through a lot of listings.