These steps will help with troubleshooting why your recently uploaded site may not be showing.
Hosting Just Enabled
When you first enable hosting, it can take several hours for the change to be seen everywhere due to dns record caching by your internet service provider. This occurs only the first time due to the dns changes made to your domain to point to our hosting servers. Any uploads after that initial period will show up on your website within seconds.
Hosting Under Construction
Has it been less than 24 hours since you enabled hosting? You may be experiencing dns record caching by your internet service provider. Refer to the section above.
Default File Missing
If it has been more than 24 hours since you enabled hosting and you're seeing a page with instructions on uploading instead of your site, it means there is no default file. The default file is what's shown when someone visits your domain. You need to upload a default file (your home page) for your website to show up. It'll need to have a specific name and be uploaded to a specific location to work.
Default File Name
If you uploaded a default file, it may not have the correct name. Default files need a specific file name (ie. index.html). You can find a list of the accepted default files names at Replacing the Default File. If your default file is not named one of those, you'll need to rename it.
Default File Location
If you uploaded a default file, it may have been uploaded to a sub-folder. Default files need to be located directly under your site folder on the server. Many FTP clients will show how your files are structured on the server. If you cannot see the files on the server, use FileZilla to upload your files as it will show you what's on the server. You can upload the file to the correct location in there.