It depends whether you are an asylum seeker or a legal immigrant but a good place to start would be to go on gumtree and advertise what you can teach and how much you charge (tutoring can be pretty lucrative if you get good results from your students) and where you are. The website is:
www.gumtree.com.
Also, simply putting adverts up in newsagent windows or dropping fliers in people's letterboxes can help if you sell yourself well and truthfully. Manchester has lots of students so try and identify the student areas and target them.

Alternatively, you could register with this tutoring agency which covers Manchester:
http://www.language-school-teachers.com/default.asp?selCountry=122&txtCi...

Good luck