adds installation instructions

README.md

@@ -1,2 +1,41 @@
-# obitools
+# obitools V4
 
+*OBITools V4* is the new version of *OBITools*. They are closer to *OBITools2* than to *OBITools3*.
+They are implemented in *GO* and are tens of times faster than OBITools2.
+
+The git for *OBITools4* is available at :
+
+> https://metabarcoding.org/obitools4
+
+## Installing *OBITools V4*
+
+An installation script that compiles the new *OBITools* on your Unix-like system is available online.
+The easiest way to run it is to copy and paste the following command into your terminal
+
+```{bash}
+curl -L https://metabarcoding.org/obitools4/install.sh | bash
+```
+
+By default, the script installs the *OBITools* commands and other associated files into the `/usr/local` directory.
+The names of the commands in the new *OBITools4* are mostly identical to those in *OBITools2*.
+Therefore, installing the new *OBITools* may hide or delete the old ones. If you want both versions to be 
+available on your system, the installation script offers two options:
+
+
+Translated with www.DeepL.com/Translator (free version)
+>  -i, --install-dir       Directory where obitools are installed 
+>                          (as example use `/usr/local` not `/usr/local/bin`).
+> 
+>  -p, --obitools-prefix   Prefix added to the obitools command names if you
+>                          want to have several versions of obitools at the
+>                          same time on your system (as example `-p g` will produce 
+>                          `gobigrep` command instead of `obigrep`).
+
+You can use these options by following the installation command:
+
+```{bash}
+curl -L https://metabarcoding.org/obitools4/install.sh | \
+      bash -s -- --install-dir test_install --obitools-prefix k
+```
+
+In this case, the binaries will be installed in the `test_install` directory and all command names will be prefixed with the letter `k`. Thus `obigrep` will be named `kobigrep`.