DOC: Explain compiling of jlcaosdb

README_SETUP.md

@@ -20,5 +20,25 @@ providing binary JLL packages in the future.
    [libcaosdb](https://gitlab.com/caosdb/caosdb-cpplib) in a way that
    it is visible to cmake when compiling the wrapper classes later on.
 
+## Compile jlcaosdb
+
+Compile the wrapper code in `jlcaosdb` by 
+
+```sh
+cd jlcaosdb
+cmake -B build .
+cd build
+cmake --build .
+```
+
+Depending on your installation of the prerequisites, you may have to
+add `-DCMAKE_PREFIX_PATH=/path/to/install/dir` to the first cmake
+command. 
+
+**TODO**: Change when we have a JLL binary for jlcaosdb. If you choose
+to compile jlcaosdb in another directory than
+`caosdb-julialib/jlcaosdb/build` you will have to adapt the path that
+is given to the `@wrapmodule` macro(s) in `CaosDB.jl` before using it.
+
 **TODO**: Explain installation (with Pkg.jl), running tests,
 dependencies, etc.