After you have created the site and have the pages on your server you should be able to login to the CMS admin area. From here you should be able to see the pages in the left navigation. You can update your gallery pages by selecting them and then click on the edit link for that area. The gallery page is just an html page with no dynamic code on it. So when you edit the page you are just editing the html that is on this page and the images.
For the form page you can create the page with the form in it in DW then add the code from the page into the CMS for that page. If the form needs any php or dynamic elements then you will need to apply it to the page itself within DW.