Update README.md

README.md

 # Library Sandbox
 
+## Assembly
+ - A beamer and a monitor must be pluged to the pc (2 outputs needed for the calibration)
+ - The camera must be pluged with an usb 3.0 extension (otherwise the resolution of the frames will be lowered)
+
 ## Depedencies
  - OS : Ubuntu 18.04
  - C++ : 11.0
@@ -9,16 +13,37 @@
  - yaml-cpp : https://github.com/jbeder/yaml-cpp @commit : 9fb51534877d16597cfd94c18890d87af0879d65
  - Qt : 5.9.5
 
-## Makefiles
-Flags for the linker availible throught the variable DEP_SANDBOX in file dep.mk
+## Makefile
+ - make lib : build the librairy
+ - make apps : build the setup application
+ - make clean : clean all generated files
+
+## Makefile for applications
+Examples can be found in the project ar_sandbox_app
+
+### Compilation
+You need to specify :
+ - The path (can be relative) to the headers of the classes in the project with the parameter -I (this is an upper case i)
+
+### Linker
+You need to specify :
+ - The path (can be relative) to the generated shared object library (file .so) with the parameter -L
+ - The flag of the generated library (-lsandbox in our case)
+ - The flags of the libraries used in the project for the linker, which are availible throught the variable DEP_SANDBOX in file dep.mk
 
 ## Before launching your application
  - LD_LIBRARY_PATH must contain the path to the directory containing libsandbox.so (which is generated in /build)
- - Enter this command in the terminal executing your applications
+ - Enter the command below in the terminal executing your applications
+ - Where $REALTIVE_PATH_TO_SO is the relative path to the generated file libsandbox.so from the current path of your terminal
 
 ```
 export LD_LIBRARY_PATH=$(pwd)/$RELATIVE_PATH_TO_SO
 ```
-
- - Where $REALTIVE_PATH_TO_SO is the relative path to the generated file libsandbox.so from the current path of your terminal
  - Don't forget that LD_LIBRARY_PATH is local to each terminal
+
+
+If the ld variable is not set correctly or the library is not generated, this error will show up :
+```
+/usr/bin/ld : cannot find -lsandbox
+collect2: error: ld returned 1 exit status
+```