http://www.baladiya.gov.qa/cui/view.dox?id=1198&siteID=1
the arabic has the details with all the laws and regulations.
try it
as i remember you need
1) your Qatari ID
2) your engineering certificate( certified in your embassy and the F Ministry)
3) police clearance.
4) work experience certificates.
5)any other qualifications or certificates.

then scan them and put them in envelope and put the scanned copy in CD.
go to UPDA building in front of City center ground floor the last employee ( he is with long beard ) and very helpful man