Due to verification of various irregular data, declarations and documents, the isue of residence certificates are temporarily suspended. Only renewals scheduled at the SEF are accepted.
You can read the official comunication here.
Registration on voter registration is taken in the commissions on the Parish Councils or and Foreigners and Borders Service, getting registered in the district corresponding census to the address indicated in the valid residence title or Certificate of Registration or Certificate of Permanent Residence of Citizens of the European Union.
For more information, please read the official documentation.
(A versão portuguesa pode ser consultada aqui.)