Made some clarifications in the README file.

sky130/README

diff --git a/sky130/README b/sky130/README
index dbc28cc..059eeef 100644
--- a/sky130/README
+++ b/sky130/README
@@ -9,9 +9,14 @@
 -------------------------------------------------------------------------------
 Quick summary (TL;DR):
 
-    Prerequisite:  The Magic VLSI layout tool is used often by the
-    installation.  If you do not have it, then obtain it and install
-    with the following:
+    Prerequisites:
+
+    	sudo apt-get install python3
+
+    The Magic VLSI layout tool is used often by the installation.  If you do
+    not have it, then obtain it and install with the following:
+
+    	sudo apt-get install m4 tcsh tcl-dev tk-dev
 
 	git clone https://github.com/RTimothyEdwards/magic
 	cd magic
@@ -33,6 +38,10 @@
     with some alternative like ~/pdks, and "make install" does not need to be
     run sudo.
 
+    With he above configuration line, the PDK files will be installed into
+    the path
+		/usr/share/pdks/sky130A/
+
 -------------------------------------------------------------------------------
 Detailed instructions for the patient reader:
 -------------------------------------------------------------------------------