doc: update installation documentation

README.md

@@ -2,17 +2,28 @@
 
 Spellchecking utility to provide automatic corrected spelling for the provided input using GNU/linux ispell.
 
+## Dependencies
+
+Install `ispell` with your favorite package-manager (on manually), as long as `ispell` in available in the PATH environment variable sp will find the executable to run.
+
 ## Installation
 
 Build the tool using the following command:
 
-```bash
+```sh
 zig build -Doptimize=ReleaseFast
 ```
 
+If you wish to install it into */usr/local/* you will have to provide the prefix argument:
+
+```sh
+sudo zig build install -p /usr/local/ -DoptimizeReleaseFast
+```
+
 This was build using zig 0.12.0.dev but should work with the most recent version of zig.
 
-Add the build `sp` executable in your `PATH` environment to easily invoke the tool.
+Add the build `sp` executable in your `PATH` environment or install it using the prefix argument to easily invoke the tool.
+
 
 ## Usage
 
@@ -23,3 +34,9 @@ sp pple
 # is equivalent to
 echo pple | sp
 ```
+
+When running the installation you also install the man page for `sp`. In case you installed in */usr/local/* as the prefix argument you can simply run
+
+```sh
+man sp
+```