Update Installing the OBITools3

Installing-the-OBITools3.md

@@ -2,7 +2,7 @@ The OBITools3 are now available to download from git, and will soon be on Nix ([
 
 First, make sure you have installed: **python3, python3-venv, git, CMake**
 
-Then you can do:
+Then you can install the OBITools3 in a virtual environment:
 
 		git clone https://git.metabarcoding.org/obitools/obitools3.git
 		cd obitools3
@@ -15,3 +15,5 @@ Then you can do:
 And test the installation with:
 
 		obi test
+
+Once installed, you will need to be in the virtual environment to run commands (`source obi3-env/bin/activate`), or add the `obi` command to your `PATH`.