Welcome to the forum.
You have named your iframe name="Inline1" so all your links will point to that iframe.
The code below is for four separate links that change the content of your iframe.
Build your pages, then link to them using this type of linking.
When someone clicks the link, the target iframe changes content.
Target defines WHERE the link opens, in iframe, new window, same window...
<A href="page1.htm" target="Inline1" title="Describe the first page">Link 1</A>
<A href="page2.htm" target="Inline1" title="Describe the second!">Link 2</A>
<A href="page3.htm" target="Inline1" title="And yet a third page you want to see">Link 3</A>
<A href="page4.htm" target="Inline1" title="And of course the 4th page">Link 4</A>