PHP is a server-side scripting language, it is used to preprocess data such as text/html and images.
There is no way to "convert" php to html. PHP files is basically just text/html files, (usually) with the .php extension, which includes server-side scripting, this scripting is not normally visible to the browser/user-agent visiting the site.
HTML is a markup language, which is now mostly used in combination with CSS to seperate content from style, the HTML is used to "markup" the sections and text in the page, while the CSS is used to create the layout.
You are not suposed to blindly copy other peoples layouts, or use templates whitout knowing what is going on behind the scenes. I highly recommend that you take the time to learn HTML + CSS, before you take use of such templates, there are websites like http://www.brugbart.com/ and http://www.w3schools.com/ holding tutorials/references.
If you are using a WYSIWYG editor, then i recommend you use templates made specifically for your editor, otherwhise you might end up with invalid code, I.E. incorrect usage of tags, and/or attributes. Also note that some editors are simply broken, and not of any practical use, an example would be the now discontinued MS frontpage.
Editors like frontpage is/where only useful when you wanted to publish a document in a hurry, or when you didn't care much about the end-result.
All you need to create/edit a website is a text-editor like notepad, it is a common mistake to think you should use "editors". All you really need is available for free on the internet. Some of these applications include features such as autocomplete, syntax highlighting, and tabbed editing.
I mostly just use notepad, and for syntax highlighting notepad++, if interested you can get it here: http://notepad-plus.sourceforge.net/uk/site.htm
Its important that the Markup is free from errors, you can check the markup from errors using the W3C HTML Validation Service - http://validator.w3.org/
You should also aim for valid CSS, but some intended errors doesn't matter much, those would include hacks for a specific browser. The CSS validator is found at: http://jigsaw.w3.org/css-validator/