Extension of HSMP visa

[nasreen]

I am an architect qualified from Bangladesh.I got HSMP visa with my two daughter and husband, who are my dependent, on 28th September 2005.I came in UK on 24th of November 2005. From then I tried to get a job in my related field but failed due to lack of experience of UK.Atlast at the end of Februrary2006 I got 3days and then 7days contract job as an AutoCAD operator after that again jobless.However now I got a job out of London as an architectural assistant where I am going to join on 15th of May 2006.I came in UK only with my youngest daughter, my elder daughter and my husband are remain in Bangladesh who will come in UK on the begining of July 2006.My question is for the extention of HSMP visa for the next three years with my family when I will apply, from where and how and what are the procedure and what necessary papers will be needed? Wating for the answer from senior members.

Regards
Nasreen