added new document about adding new files

doc/gitlab-basics/README.md

@@ -17,3 +17,5 @@ Step-by-step guides on the basics of working with Git and GitLab.
 * [Create a branch](create-branch.md)
 * [Fork a project](fork-project.md)
+
+* [Add a file](add-file.md)

doc/gitlab-basics/add-file.md

+# How to add a file
+
+You can create a file in your [shell](command-line-commands.md) or in GitLab.
+
+To create a file in GitLab, sign in to [GitLab.com](https://gitlab.com).
+
+Select a project on the right side of your screen:
+
+![Select a project](basicsimages/select_project.png)
+
+[Create a branch](create-branch.md).
+
+Go to the directory where you'd like to add the file and click on the "+" sign next to the name of the project and directory:
+
+![Create a file](basicsimages/create_file.png)
+
+Add a name to your file, use .md or .html at the end, depending on which markup language you'd like to use (you can't add spaces, so you can use hyphens or underscores):
+
+![File name](basicsimages/file_name.png)
+
+Add all the information that you'd like to include in your file:
+
+![Add information](basicsimages/white_space.png)
+
+Add a commit message based on what you just added and then click on "commit changes":
+
+![Commit changes](basicsimages/commit_changes.png)
+
+### Note
+Besides its regular files, every directory needs a README.md or README.html file which works like an index, telling
+what the directory is about. It's the first document you'll find when you open a directory.