Show Post Preview on Main Page

Hey everyone,
I know that this have been a topic many times on here, but I can’t seem to find a solution that works for me:

1) I’m trying to have my theme only display a preview post and one pic on the homepage for each post.
Currently my wordpress blog looks like this and
here’s my blog on blogger with the same theme. This is how I want my wordpress blog to look.

I know a lot of people suggest changing the_content to the_excerpt but I can’t find that anywhere. I couldn’t find it in index.php, some suggest finding it in content.php, which is not one of my template options.

2) I’m also trying to move the post info (category, date posted, and number of comments) from the left of the post to the top of the post. I’ve also tried researching this, but there doesn’t seem to be a good amount of info on this.

Any help with these issues would be greatly appreciated.
Thanks in advance!