docs: update use_quantization.md part 1

docs/user/howto/use_quantization.md

@@ -1,9 +1,41 @@
-```{warning}
-FIXME(Jordan): do this
-```
-
 # Using Quantization in Concrete Framework
 
-(as a user)
+In this section we detail some usage of [quantization](../explanation/quantization.md) as implemented in Concrete.
 
-explain issues the user will still fail and that we plan to research on it
+## Quantization Basics
+
+The very basic purpose of the quantization is to convert floating point values to integers. We can apply such conversion using `QuantizedArray` available in `concrete.quantization`. 
+
+`QuantizedArray` takes 2 arguments:
+- `n_bits` that defines the precision of the quantization. Currently, `n_bits` is limited to 7, due to some ConcreteLib limits.
+- `values` that will be converted to integers
+
+```python
+from concrete.quantization import QuantizedArray
+import numpy
+numpy.random.seed(0)
+A = numpy.random.uniform(-2, 2, 10)
+# array([ 0.19525402,  0.86075747,  0.4110535,  0.17953273, -0.3053808,
+#         0.58357645, -0.24965115,  1.567092 ,  1.85465104, -0.46623392])
+q_A = QuantizedArray(7, A)
+q_A.qvalues
+# array([ 37,          73,          48,         36,          9,  
+#         58,          12,          112,        127,         0])
+# the quantized integers values from A.
+q_A.scale
+# 0.018274684777173276, the scale S.
+q_A.zero_point 
+# 26, the zero point Z.
+q_A.dequant()
+# array([ 0.20102153,  0.85891018,  0.40204307,  0.18274685, -0.31066964,
+#         0.58478991, -0.25584559,  1.57162289,  1.84574316, -0.4751418 ])
+# Dequantized values.
+```
+
+## Operations in the Quantized Realm
+
+## Why are the scale and zero point not a problem ?
+
+## Compilation
+
+## Future releases