Display Author's Name Next to Post Date?

My current theme is not displaying the Author’s name.

I’d like it to:

1) Display the Author’s Name (and)

2) Have the Author’s Name ‘linked’ .. so that when people click on the name, it brings up all Posts by that author.

Currently, a post looks like this – Title / Date / Number of Comments:

https://bit.ly/crB2cM

This is my current theme:

https://www.ads-software.com/extend/themes/modern-style

It’s a free theme. I’ve contacted the designer’s home page, but they won’t provide any support without a paid membership.

What code can I change to get a ‘linkable’ Author’s Name displayed in my post header?

Thanks.