when you are in the neighbourhood, click on the house
you will get the enter option and on the left hand side a little snowflake looking icon
click on that and it will package and save your house
you will then find it in the packagedlots folder of your game documents folder
open that and right click on the package which has now been created and open it with Clean Installer. you will need this to remove hacks, recolours and other custom content you don't want in there.
if you don't have
Clean Installer i recommend you take your downloads folder totally out of the game before you package your lot. in fact do this anyway, to be certain
once you have packaged your lot you can put the downloads folder back in. doing it this way will give you a clean package which you wont have to do anything else with except upload it to your site
if using Clean Installer, you can then repackage your lot by clicking the save as button at the bottom of the program window and rename it or add a couple of letters to the filename. you will get 2 copies, use the renamed copy
those are the 2 ways i do it, but someone else might come along with more suggestions
i can't help you with getting it onto your site because i don't know how your host handles uploads