I don't have an "Appearance > Extras" menu in my sidebar

That’s on WordPress.com hosted blogs not self-hosted.

You can add it to your self-hosted www.ads-software.com site by pasting the code generated at https://twitter.com/goodies/tweetbutton into an appropriate place in your theme. If that’s a bit tricky for you, it should work just as well pasted into a text widget.

Thanks so much.

I just started managing this blog for the company I work for, so I’m a pretty big noob. If I’m not mistaken, text widgets can only be applied to the sidebar, correct? What about if I’m looking to include the button at the bottom of individual posts, similar to the Facebook Like button plugin? Is this possible?

Thanks again.

Just seen a tweet from wpbeginner – they’ve just published a tutorial covering exactly this: https://www.wpbeginner.com/wp-tutorials/how-to-add-twitters-official-tweet-button-in-wordpress/

Now there’s a plugin https://www.ads-software.com/extend/plugins/wp-tweet/