grab thumbnail from first post in category & permalink to category

Ok lets get streight to the point: im working on a direct tv series watch website.
I got the summery for each series up, but i want to have a poster near the summary, something like this:
example
as you can see from the example above, theres a poster of the said series near the summary.
I want to accomplish this by grabbing the thumbnail from the first post in the category of the said series, and place it near the theme.

the thing is, i am kinda new to php, i got the category description up but i just cant seem to figure out how to perform this sort of thing.

another thing i am having trouble doing is making a permalink from a post to a category, mean that when i press on a post’s name(or thumbnail) it will redirect me to a category. i want to make this so that when new series come out, i can do a new series section that will have the name and thumbnail(the thumbnail will be a poster of the series) so that when people press it they will be redirected automaticly to the category of the series.

Ive tried using Hikari Category Permalink but it didint work(didint even do anything…)

Sorry for the hard requests, any help please? :]