One way to create a new style sheet (internal or external) is to right-click on your page. There is an option "CSS Styles". If you click that, it will show you that you have "None" (unless you've already been using styles, whether you knew it or not).
Figure 23 - Click to Enlarge
Another option is to click on File, then New... This is for external style sheets.
Figure 24
Then it will ask you to choose a new type of page to start building from. You want to select CSS.
Figure 25 - Click to Enlarge
You can start "New..." styles. This will make them Internal Styles, and if you change on thing on one page, it will NOT change every page that has the same style. This is more for making differences amongst your pages.
Figure 26
When you are here, it will automatically start a new style sheet unless you check that you want it in "This document only." Give the code a name. For example, on the next part, "Backgrounds," I'm just going to label it Background. But you may end up doing more than just changing the background, so maybe you'll want to name it something like, "My Page".
Figure 27 - Click to Enlarge
You can make a plethora of changes here.
Once you've already started your CSS file, you can attach it. Review Figure 23 at the top of the page, and notice it will have Attach.... Here, you can link to the CSS file you've made. Point to it, select it, using Browse... and click OK.
Figure 28
The essential coding for external style sheets is:
<link rel="stylesheet" type="text/css" href="style.css" />
The href=" ~ " is the part that you would change, depending on what your file was named and where it was located. If it's in a previous folder, then you would just put ../ before style.css, but if it was in the next folder, it would look something like folder/style.css, etc. Once you're playing within the file, the coding would look like the same thing that is between the <style> </style> tags of the first example.
External style sheets are useful when you want uniformity among your pages. Then, when you change one thing, it will adjust for all pages linked to it. It's also a good catch-all for formatting, so you're not looking around for that one mistake, or having one page off from the rest.
Be sure that when you have made your new CSS file, that you save it. It's recommended that you save the file before you Attach it to a page.
Figure 29 - Click to Enlarge
Tip: On a PC, CTRL+S will Save, CTR+Shift+S will Save As. On a Mac, Alt+S will Save, Alt+CTRL+S will Save As.