update README

README.md

@@ -13,26 +13,37 @@ This version is known to compile with:
 If you need to work with Coq 8.5, please check out the
 [iris-3.0 branch](https://gitlab.mpi-sws.org/FP/iris-coq/tree/iris-3.0).
 
-The easiest way to install the correct versions of the dependencies is through
-opam.  You will need the Coq and Iris opam repositories:
+## Installing via opam
+
+To obtain the latest stable release via opam, you have to add the Coq opam
+repository:
 
     opam repo add coq-released https://coq.inria.fr/opam/released
+
+Then you can do `opam install coq-iris`.
+
+To obtain a development version, add the Iris opam repository:
+
     opam repo add iris-dev https://gitlab.mpi-sws.org/FP/opam-dev.git
 
-Once you got opam set up, run `make build-dep` to install the right versions
-of the dependencies.
+## Building from source
 
-## Updating
+When building Iris from source, we recommend to use opam for installing Iris's dependencies.
+This requires the following two repositories:
 
-After doing `git pull`, the development may fail to compile because of outdated
-dependencies.  To fix that, please run `opam update` followed by
-`make build-dep`.
+    opam repo add coq-released https://coq.inria.fr/opam/released
+    opam repo add iris-dev https://gitlab.mpi-sws.org/FP/opam-dev.git
 
-## Building
+Once you got opam set up, run `make build-dep` to install the right versions
+of the dependencies.
 
 Run `make -jN` to build the full development, where `N` is the number of your
 CPU cores.
 
+To update Iris, do `git pull`.  After an update, the development may fail to
+compile because of outdated dependencies.  To fix that, please run `opam update`
+followed by `make build-dep`.
+
 ## Directory Structure
 
 * The folder [algebra](theories/algebra) contains the COFE and CMRA