Update README.md

README.md

 # ITCPG
 
 [![Build Status](https://gitlab.pik-potsdam.de/stuermer/ITCPG.jl/badges/master/pipeline.svg)](https://gitlab.pik-potsdam.de/stuermer/ITCPG.jl/pipelines)
+
+A Julia package for simulating the Impact of Tropical Cyclones on Power Grids (ITCPG). The power grid is modeled via AC power flow equations that are solved using [PowerModels.jl](https://github.com/lanl-ansi/PowerModels.jl).
+
+## Installation
+
+Add the package using Julia's package manager and the URL to this repository:
+
+```julia-repl
+(v1.3) pkg> add https://gitlab.pik-potsdam.de/stuermer/itcpg.jl
+```
+
+Afterwards, `using ITCPG` should allow you to use all exported functions.
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