Very straight forward, just select the dropshippers that most interest you. Then contact them to clarify anything further you require, if happy, then just open an account with them and you're ready to start trading, Things like images and product descriptions, ask your supplier/s to provide those for you.
Regarding BG, they are an approved supplier in our directory. Charlie is always on top of customer support for BG here on the forum, so if you're interested in learning more about them, I would suggest shooting them a PM or emailing them direct on the site for further.
Regarding your question about SaleHoo, can you clarify for us please, not quite sure what you mean.
Regarding dropshipping. In essence, you are an agent selling the supplier's products. So you market the products at your price, then the customer buys from you. Once you have the order, you process that through your account with the supplier. You then pay them and they send the product direct to your customer (blind) Meaning no invoice or branding of their name, so your customer is not in formed where the item comes from and protects you.
Regarding templates for the store, you can contact Link hidden: Login to view
and the staff there will be able to assist you with that.