Easy edits based off of observing Eden go thru tutorials (gatsbyjs#3501)

A few typo corrections and clarified wording. There are more big changes to address later.

docs/tutorial/part-one/index.md

@@ -15,16 +15,14 @@ Sit down, buckle up, and let's get going!
 ## Check your development environment
 
 Let's check first that you have everything set up to start creating with Gatsby.
-You will need a recent version of [Node.js](https://nodejs.org) installed.
+You will need a recent version of Node.js installed.
 
 Node.js is a programming tool for running JavaScript on servers and in your
 computer's terminal. Gatsby is built using Node.js.
 
 Open a terminal window. See
-[these instructions](http://www.macworld.co.uk/feature/mac-software/how-use-terminal-on-mac-3608274/)
-for Mac users and
-[these other instructions](https://www.quora.com/How-do-I-open-terminal-in-windows)
-for Windows users. In your terminal window, type `node --version` then `npm --version`.
+[terminal instructions for Mac users](http://www.macworld.co.uk/feature/mac-software/how-use-terminal-on-mac-3608274/) and
+[terminal instructions for Windows users](https://www.quora.com/How-do-I-open-terminal-in-windows). In your terminal window, type `node --version` and hit ENTER, then `npm --version` and hit ENTER.
 
 You should see something like:
 
@@ -43,7 +41,7 @@ There are several official starters and many others contributed from the Gatsby
 community! [See the Starters page for the full list](/docs/gatsby-starters/).
 
 To install a starter, first install Gatsby's terminal program by typing the
-following command into the a terminal window and hit ENTER.
+following command into the terminal window and hit ENTER.
 
 ```sh
 npm install --global gatsby-cli
@@ -93,8 +91,7 @@ open the folder on your computer called "tutorial-part-one," which was
 automatically created when you ran the `gatsby new` terminal command above.
 
 Once you've opened the "tutorial-part-one" folder in your code editing
-software, it's time to edit your website. In the code editing software, you'll
-need to find `src/pages/index.js`. Once you find that, try changing "Hello
+software, it's time to edit your website. You'll see groups of directories and files; find the file in this location: `src/pages/index.js`. Once you find that, try changing "Hello
 world!" in the page component to "Hello Gatsby!". Once you save that change, the text in your browser
 should change within a second.