I'm a newbie to LB too but I've done a lot with Btc in the past (mining etc). I now use Bitpander to buy and send Btc, once I'd got my account set up (verification was really quick but you do need ID) I just used a credit card to put money in my £ wallet than you can transfer it to Btc and the bitcoin sits in your Bitcoin wallet (auto created). You can then transfer Btc to LB sellers via the link it generates. Make sure you are logged in to LB when you place the order otherwise you can't track it or easily message the seller. Note it can take 20 minutes for the block chain to update after sending the Btc so don't freak out, it will update.
I did have a local Btc wallet on my pc but this isn't necessary for LB transactions, it does offer greater security if you were to hold a high value wallet for the medium to long term.