I have yacoin-qt up and running but there i no mining tab as there is with litecoin for example.
or does it only appear once i have downloaded the blockchain>?
No - the mining icon (like Litecoin) is not available in the client. If you have everything up and running and have your config file setup, just add gen=1 and you should be good.
The config file should be
rpcuser=username <--- change this
rpcpassword=password <--- change this
rpcallowip=127.0.0.1
gen=1
Also: Don't encrypt your wallet if you're going to mine.
http://www.youtube.com/watch?v=Hn7B5FdwBK8
But seriously, what is a config file and where do I put it? When I said noob to mining, think "no fucking idea".