Getting-started.md

+This instructions can also be found in the *README*. The software needs to be compiled (see [CAXS installation page]()).
+
+# Setup
+1. Put [GEISA 2015](http://cds-espri.ipsl.fr/cgi-bin/geisa/geisa2015_format) - formatted lines data of the species of your choice inside the _data/lines_ directory. These data needs to contains **at least** GEISA parameters A to D. If your species name is "speciesName", the lines file needs to be named "speciesName.dat".
+2. Copy the file _data/species/H2O.nml_, rename the copy as _speciesName.nml_ and edit it to suit your needs. ("nml" is the extension used for [Fortran namelists](http://jules-lsm.github.io/vn4.3/namelists/intro.html)).
+3. Edit the file _inputs/input_parameters.nml_ to suit your needs. **Be careful:** 
+    - `n_levels` must match the number of values of `pressure_space`;
+    - if `use_profile_mode` is `True`, `n_levels` must also match the number of values of `temperature_space`;
+    - if `use_profile_mode` is `False`, `size_thermospace` must match the number of values of `temperature_space`;
+    - `n_species` must match the number of values of `species_names` and `species_vmr`;
+    - `species_names` values must be the names used for the _data/lines_ and _data/species_files.
+
+# Setup for Rey et al. 2017 CH4 lines
+1. Get Rey et al. CH4 lines from [here](http://theorets.tsu.ru/molecules.ch4.hybrid) (both strong lines and weak lines).
+2. Put the lines files inside the _data/lines/CH4_ directory (`mkdir` it if it doesn't exists yet).
+3. Follow the "setup" steps above from step 2. **Be sure to exactly write "CH4" for the _data/species_ file name and for the species name**.
+
+# Running CAXS
+1. Open a terminal.
+2. `cd` yourself into CAXS' _bin_ directory.
+3. Launch the calculations by executing (replace `X` by the number of processes you want to use):
+    ```bash
+    mpiexec -np X caxs.exe
+    ```
+    Alternatively, if you want to use only 1 process, you can execute (you still need to have OpenMPI installed):
+    ```bash
+    ./caxs.exe
+    ```
+4. By default, at the end of the calculations, the results are stored in the _outputs_ directory.
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