In order to upload your newly-created gallery to your web space, you'll need some information which should be provided by your ISP. You may need to do some hunting around on their website, but somewhere you should be able to find instructions for uploading via FTP. You need a "host name" or "server name", which will usually look something like "ftp.yourispname.co.uk". You also need a username and password, which may be the same as the username and password that you use to connect to your email service, or may have been assigned to you or chosen by you when you signed up for the free webspace with your ISP. If you really can't find this information, you may need to make a call to your ISP's technical help line.
Once you have the host name, username and password, start up your FTP Client program. You need to enter the login details to make a new connection. If you're using AceFTP, click on the File menu and select Connect. In the window that appears, double-click on New Site Profile. In the dialogue that appears, enter the Server (host name), User ID (username) and password, and give your connection a name, preferably the name of your site. Leave all the other settings in their default state. Click Next to go on to the following page, which will ask you to name local and host folders. You don't need to enter anything here, just click Finish to complete the dialogue and you should see the new connection appear in the connection window.
Double-click on your new connection to link directly to the server where you will upload your site. You'll see some information scroll past in the top window, a tone will alert you that the connection has been made, and aboive the right-hand window you should see a folder called "htdocs". This is the folder on the remote server where your website will live. There may already be a sub-folder in the htdocs folder; if there is just ignore it.
In the left-hand window, navigate to the folder where you had Picasa export your gallery files. You should be able to see a folder named "Images", another called "Thumbnails" and a file called "Index", as well as a lot of other files. You need to copy all of these files into the htdocs folder on the server, so highlight all the files and folders by clicking on one and them pressing CTRL + A, and then click on the button between the two windows with the left-to-right arrow. Your file transfer will begin, and depending on the amount of files and the speed of your connection it may take several minutes to complete. AceFTP will make a noise when it's done.
And there you are, you've successfully published your first website, and it didn't hurt a bit. To see it live, open your web browser (you're looking at it right now) and go to the URL of your web space as provided by your ISP. It's probably something like www.yourusername.yourispname.co.uk. Here's one I made earlier: Dunkeswell Air Show gallery. It's very basic at the moment, but you can start off with something like this and then experiment. You can delete and change files on the server and move files from your PC to your htdocs folder as often as you like, so feel free to play with it. As long as you keep a backup of your site on your home PC, if you break something you can always delete it all and upload it again.
There are a number of other programs available that provide easy ways to make good-looking websites, and they all produce the same type of files that can be uploaded to your htdocs folder for viewing on the internet. If you want to take things even further, it doesn't cost much to buy your own domain name from a domain registry company such as UKReg, and you can buy a web hosting package for just a few pounds a month that will give you far more storage space for bigger galleries, plus other features such as personalised email addresses and password protection for private files. Just don't go starting any technology review sites, ok?