Update README

README.md

@@ -3,26 +3,17 @@
 [![Dev](https://img.shields.io/badge/docs-dev-blue.svg)](https://tensor4all.github.io/Quantics.jl/dev)
 [![CI](https://github.com/tensor4all/Quantics.jl/actions/workflows/CI.yml/badge.svg)](https://github.com/tensor4all/Quantics.jl/actions/workflows/CI.yml)
 
-## Prerequisites
+This library provides a high-level interface to manipulate quantics tensor train (QTT) format in Julia such as Fourier transform, convolution, and matrix-vector multiplication.
+This library is based on `ITensors.jl`.
 
-```console
-cd path/to/Quantics.jl
-$ julia --project=@.
-               _
-   _       _ _(_)_     |  Documentation: https://docs.julialang.org
-  (_)     | (_) (_)    |
-   _ _   _| |_  __ _   |  Type "?" for help, "]?" for Pkg help.
-  | | | | | | |/ _` |  |
-  | | |_| | | | (_| |  |  Version 1.9.4 (2023-11-14)
- _/ |\__'_|_|_|\__'_|  |  Official https://julialang.org/ release
-|__/                   |
+## Installation
 
-julia> using Pkg; Pkg.instantiate()
-```
-
-## Test this package
+The following will install `Quantics.jl`:
 
-```console
-$ julia --project=@. -e 'using Pkg; Pkg.test()'
+```julia
+julia> using Pkg; Pkg.add("Quantics.jl")
 ```
 
+## Usage
+
+Please refer to the [documentation](https://tensor4all.github.io/Quantics.jl/) for usage.