Your original post didn't explain what you were stuck on in the process of reading the three topics.
I don't know if changing the images will be fixed soon but I will make a code for it later.
Changing your css isn't bugged, you just need knowledge of how to edit it.
Creating an ezPortal only creates another page for your forum, you need to create ezBlocks to display content on it.
I don't think there is a way of hiding a certain category however if you just want to link a few topics from your tabs, you can create new webpages using the Page Manager.