How to add a new page with Seamonkey Composer
Open SeaMonkey by double clicking on the desktop icon . The following window will open.
In the bottom left corner of the SeaMonkey window is a row of 5 icons.
If you hover over them with your mouse, you can see what each icon represents.
Click on the Composer icon (the middle one) to open the editor window:
Click on the "open" icon at the top left of the window, navigate to your local web site directory and select the appropriate "xxx .htm" file you want to edit.
If you are crearting a new page, open your site template file if you have one (e.g. my-site-template.htm)
Save the template using File > Save-As and name the file e.g. "your-new-filename.htm"
Edit your new file as necessary.
Save the file.
Preview your new web page in the built in Seamonkey browser by clicking on the "Browse" button on the top menu bar.
Upload new file to the top level directory on your server using Fileziller (or what ever ftp tool you prefer)
Upload any new photos and images you have included in your new page to the relevent directory (e.g. images) on your server.
View your live site in your browser and check it all looks OK.