Since SpectreRF is a license option to spectre (the simulator is the same), you choose the analyses specific to SpectreRF from the Choose Analysis form in ADE with "spectre" selected as the simulator (e.g. pss, pac, pxf, pnoise, psp, pstb, qpss, qpac, qpxf, qpnoise qpsp, envlp).Originally posted in cdnusers.org by adbeckett
SpectreRF is covered in cdsdoc, as is VerilogA. (SpectreHDL is obsolete). If you can't run cdsdoc for some reason, try to get that sorted out, but otherwise look in /doc, in particular at spectreRF/spectreRF.pdf , spectreRFTheory/spectreRFTheory.pdf and veriaref/veriaref.pdf .
I'd also recommend the book http://www.designers-guide.org/Books/#Kundert-2004 as a good place to learn Verilog-A.
Diva and Assura are different, but do have some similarities in the rule decks, and have some common implementation. But they are different tools.