Registering with an employment agency involves filling out forms which ask questions about your experience, personality and other details. The agency also takes a copy of your resume. It is often left up to you to sort through the job vacancies that are registered with the agency, but the agency may match you to jobs themselves. If not, you can express your interest in a position. The employment agency will decide whether you are suited to the position and arrange processes such as interviews with the employer. You should aim to place your name with as many agencies as possible.
The employer is to pay the agency for recruitment purposes, so be aware that you should not be charged for using such services.
You will find a list of recruitment agencies via CareerHub > Links.