Need advice about ranking and keywords in website

Hello,
I'm newbie at IM and I'm moving towards to try internet marketing. I found niche with low authority websites (following very good tutorials here on BlackHatWorld), bought domain and hosting. I want to say really big thanks to this website and it's very helpful and friendly community. Although members here use black methods to make money, only their hats are black, but not their hearts! Because you sacrifice your time writing very long and time consuming methods/tutorials, giving good advice and helping each other.
I have read many various tutorials here, but still I feel that I need to clear some things in my head to be sure.
Suppose I'm targeting for keywords "installing motherboard in pc". Domain, keywords and content text below are made up.
1. Main page. Q: What to place here for better ranking/seo ?
Site Logo section (small header(no big banner picture).
Horizontal Navigation menu.
Content Area
Footer.
In Content area now I have text area : Welcome to fixyourpc.com Here you will learn how to install motherboard in pc and other related information about fixing your pc.
Then post list with 6 articles excerpt and Read More, and below them there's link View More Articles. If user clicks that, he's redirected to page with all articles listed.
Q: Is it good option or should I list all articles in Main Page ?
And for now that's it for Main Page. I will look for ways to improve it more, if you have suggestions about it, I would be really grateful!

2. Keywords and how google treats keywords. For example I wrote an article with title "install motherboard in pc". As I read that you should mention ~3% of keywords in you article, so in 100 words article I should use "install motherboard in pc" 3 times? Suppose that's the keywords with low authority websites in google ranking. I wrote an article and named it "Install motherboard in pc". How much I can variate this keyword, to still rank for it? For example if I use "install motherboard your in pc" instead of "install motherboard in pc" would it be bad?
Now I need another article, but I can't call it "Install motherboard in pc" too. How to determine how to variate with "Install motherboard in pc" keywords for new articles to rank in google with those keywords? Suppose google suggests search term/keyword "install new motherboard in pc with screwdriver". I write an article with that title, will it help to rank my page for "Install motherboard in pc", or google will treat "install new motherboard in pc with screwdriver" as a different keyword and won't help much in ranking with my main keyword?
And suppose keywords "Install motherboard in pc for woman", "Install motherboard in pc as woman" is very saturated and has high authority websites in google ranking. But for example "Install motherboard in pc woman" has good volume and low authority sites ranking. I don't get how to rank with those keywords, maybe you can use "Install motherboard in pc woman" in title, but it would be stupid to write precisely "Install motherboard in pc woman" in article itself, and you can not use "Install motherboard in pc for/to/as woman" because there's high authority sites ranking with these.
I hope I didn't bore you very much. Thank you for your time!

Hello,
I read my question and I think maybe it's too long, badly structured and not very clear. I can't edit it, so I will make my questions shorter and more direct here.
1. What should I put it main page to help me rank with particular keyword?
2. Articles. For examples if I am ranking for "install motherboard in pc". I wrote an article with title "Install Motherboard In PC". I write an article using that keyword ~3 times for 100 words, also write long tale and LSI keywords. I have one article.
What should I write in upcoming articles to rank for "install motherboard in pc" keyword? Will it be good to write articles like "How to choose motherboard for your PC" , "Why do you need good motherboard in your PC" ?