Clarify testing instructions.

wiki/src/contribute/how/testing.mdwn

@@ -4,4 +4,8 @@ Please try release candidates for testing purposes.
 
 **Do not rely on these for anything. No guarantee, blablabla.**
 
-The release candidates can be downloaded [[here|http://dl.amnesia.boum.org/tails/testing/]]. See [[testing guidelines|contribute/release_process/test/]].
+The release candidates are announced on [[news]] and can be downloaded
+[there](http://dl.amnesia.boum.org/tails/testing/).
+
+If you don't know what to test, see our [[testing
+guidelines|contribute/release_process/test/]].