Updgrade guide (#9)

README.md

@@ -6,8 +6,12 @@
 [![Coverage](https://codecov.io/gh/ITensor/ITensorMPS.jl/branch/main/graph/badge.svg)](https://codecov.io/gh/ITensor/ITensorMPS.jl)
 [![Code Style: Blue](https://img.shields.io/badge/code%20style-blue-4495d1.svg)](https://github.com/invenia/BlueStyle)
 
-MPS and MPO methods based on ITensor (ITensors.jl).
+Finite MPS and MPO methods based on ITensor (ITensors.jl).
 
-This package currently re-exports the MPS and MPO functionality of the [ITensors.jl](https://github.com/ITensor/ITensors.jl) and [ITensorTDVP.jl](https://github.com/ITensor/ITensorTDVP.jl) packages, including applications like DMRG, TDVP, applying MPO to MPS, applying gates, etc.
+This package currently re-exports the MPS and MPO functionality of the [ITensors.jl](https://github.com/ITensor/ITensors.jl) and [ITensorTDVP.jl](https://github.com/ITensor/ITensorTDVP.jl) packages, including applications like DMRG, TDVP, applying MPO to MPS, applying gates to MPS and MPO, etc.
 
-The goal will be to move the MPS and MPO code from those packages into this repository, and for the `ITensorMPS.jl` package to be the primary entry point for the finite MPS and MPO functionality of ITensor.
+See the [ITensor documentation](https://itensor.github.io/ITensors.jl/dev) and the [ITensorTDVP.jl examples](https://github.com/ITensor/ITensorTDVP.jl/tree/main/examples) for guides and examples on using this package.
+
+## Upgrade guide
+
+The goal will be to move the MPS and MPO code from the ITensors.jl package, along with all of the code from the [ITensorTDVP.jl](https://github.com/ITensor/ITensorTDVP.jl) package, into this repository. If you are using any MPS/MPO functionality of ITensors.jl, such as the `MPS` and `MPO` types or constructors thereof (like `randomMPS`), `OpSum`, `siteinds`, `dmrg`, `apply`, etc. you should install the ITensorMPS.jl package with `import Pkg; Pkg.add("ITensorMPS")` and add `using ITensorMPS` to your code. Additionally, if you are currently using [ITensorTDVP.jl](https://github.com/ITensor/ITensorTDVP.jl), you should replace `using ITensorTDVP` with `using ITensorMPS` in your codes.