Updated runtime files.
diff --git a/READMEdir/README_mac.txt b/READMEdir/README_mac.txt
index 82279ae..cdef1a2 100644
--- a/READMEdir/README_mac.txt
+++ b/READMEdir/README_mac.txt
@@ -4,5 +4,25 @@
See "README.txt" for general information about Vim.
-Sorry, this text still needs to be written!
+To build from sources, like on Unix
+1. Get the build tools: "clang" and "make". These can be installed with the
+ "CommandLineTools" package. If you don't have one, do
+ xcode-select --install
+ Just like for any software development with OS X.
+
+2. Get the source code. Best is to use git (which you need to install first),
+ see http://www.vim.org/git.php
+ Or you can download and unpack the Unix tar archive, see
+ http://www.vim.org/download.php
+
+3. Go to the top directory of the source tree, do
+ make
+ sudo make install
+ A newly built vim will be installed under "/usr/local".
+
+
+If you can't manage to make this work, there is a fallback using Homebrew:
+
+1. Install Homebrew from http://brew.sh/
+2. Install latest Vim with: brew install vim