Uploading blog

Hi Guys,

I am new to this. I have already built a webpress website using the online tools. So I have a website on the wordpress servers. I now wanted to modify the blog site so I installed worpress on my mac which is working fine. The question I have this.

1) is it possible to download (import) the folder which is holding my already up and running blog site

2) If I can do that is it possible then after i modify the files loccaly to upload (export) them back to the wordpress servers so that they replace my old blog site.

Thank you for the help in advance guys,
Emreal.