docs(readme): description to how use the project

README.md

@@ -2,4 +2,28 @@
 
 # Calculator
 
-a c++ calculator to handle infinite numbers
+a c++ calculator to handle infinite numbers
+
+## How to use
+
+### 1. Create a directory build and go inside
+```bash
+mkdir build && cd build/
+```
+### 2. Build the project
+```bash
+cmake ..
+```
+### 3. Build the binaries
+```bash
+make
+```
+### 4. Run the project
+```bash
+# go back to the root of the project
+./johnDoe
+```
+### 5. Unit test
+```bash
+./unit_test
+```