describe how to set params
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+# Setting Environmental Variables
+
+To set up environmental parameters or variables on Marvin it's recommended
+to use the argument ```params``` that is present on every engine actions.
+
+## Setting up params
+You may edit the file *engine.params* that is located at the root directory
+of your engine. You must insert params as a dictionary:
+
+```
+{
+ "login" : "marvin",
+ "password": "123455"
+}
+```
+
+## Loading params
+Params are loaded as an argument on your engine execution. Then, inside your
+code you must do ```params.get("login")``` or ```params["login"]``` to access
+those variables.
+
+## Samples
+* [Example of *engine.params* file](https://github.com/marvin-ai/marvin-public-engines/blob/master/iris-species-engine/engine.params)
+* [Example of loading params on **Acquisitor and Cleaner**](https://github.com/marvin-ai/marvin-public-engines/blob/master/iris-species-engine/marvin_iris_species_engine/data_handler/acquisitor_and_cleaner.py)
+
+<div class="alert alert-info">
+Notice that if you are running your actions using an API, you may alse set params at
+the the API body. These params will overwrite the <i>engine.params</i> file.
+</div>
