v0.3.2 will not be able to mine on the fullnet. You need v0.3.3.
Mining has been disabled from the UI, but can still be done using the "siac" command-line utility packaged with Sia:
https://github.com/NebulousLabs/Sia/releases/v0.3.3To CPU mine, first run "siad", then run "siac miner start [threads]" from a separate terminal.
Unfortunately siac will not display your CPU hash rate, but you can find it by viewing to localhost:9980/miner/status in your browser.
Siad v0.3.3 + Sia-GUI v0.3.2 works fine. I'm find block №101. And now got ~300k sc.
Sorry, my mistake, I thought you meant siad v0.3.2. Still, I don't recommend running different versions of Sia-UI/siad because the API has changed and may cause unexpected behavior.
another question: is upnp support included? if yes, is it enabled by default?
because when I click "announce", it says I need to open the port.
No UPnP support yet, sorry. You will need to forward your ports manually. (In fact, we encourage everyone to do this, because it improves overall network health.) The default ports are 9981 and 9982.