displaying only 6 posts at a time on the front page:
in the dashboard go to "Settings" click on "Reading" and enter 6 into the field labeled "Blog pages show at most". when you look at the front page there should be a button or some text at the bottom that leads to the rest of the posts, it will say 'more' or 'earlier' or something.
a second page the displays all your posts archived monthly:
you need what's called an Archive Page. not all themes have one of these by default but the way to find it is this: in the dashboard go to "Pages" and click on the page you want for this purpose (if you haven't made one already then make one now). in the right hand column there is a box called "Page Attributes". if your theme already has a default Archives template it will be in this box in the drop-down under "Template". if your theme does NOT have a "Template" drop-down that means there are no other page template options.
if this is the case, id suggest you do some searching on the topic of creating an Archive Template. it might be a bit of teaching yourself some stuff but on the whole not that hard.