depending on the size of your current site, designing your new site and simply copy and pasting your content may be your best option!

Hello
Firstly you need to concentrate on creating your own theme from html. Here is a how-to for that:http://www.concrete5.org/documentation/how-tos/designers/making-a-t...

After creating the theme, you can add pages from dashboard sitemap. If you wish to create any slider or anything else that is not included into Concrete5, you need to find it from C5 marketplace.http://www.concrete5.org/marketplace/addons/...

There are some add-ons which is free of cost but others you need to purchase.

Finally if you need any additional help regarding setup or anything, just shoot me a Private Message. I can help you.

Rony