hi,
i'm a post graduate student and want to do my ph.d but can not decide where to go about it?.....

Search the project database here at www.findaphd.com. Contact a supervisor, send them your CV and a covering letter, etc. Be quick about it as time is short. Also, check out Marie Curie studentships e.g. http://www.findaphd.com/clickcount.asp?fpa_id=16 .

i want to take an admission in field of medical mycology for PhD courses. i have a scholarship from ministry of Iran

Dear Badali

Search the project database here at www.findaphd.com. When you find people offering projects in the area you are interested in write to them stating the research you'd like to carry out and that you have a government scholarship. You will also need an English language qualification. See our Funding and PhDs Explained sections for links and information.