diff --git a/Installation.md b/Installation.md
index 864b806..96a7663 100644
--- a/Installation.md
+++ b/Installation.md
@@ -54,3 +54,64 @@ virtualenv .venv
 source .venv/bin/activate
 .venv/bin/pip --require-virtualenv install -r requirements.txt
 ```
+### Config file
+
+First time user? Copy the `config.py.example` file to `config.py`. This file is
+used for modifying filters and setting variables such as custom field names.
+
+```sh
+cp config.py.example config.py
+```
+
+### Set environment variables
+
+Set the following environment variables:
+
+```sh
+export ZABBIX_HOST="https://zabbix.local"
+export ZABBIX_USER="username"
+export ZABBIX_PASS="Password"
+export NETBOX_HOST="https://netbox.local"
+export NETBOX_TOKEN="secrettoken"
+```
+
+Or, you can use a Zabbix API token to login instead of using a username and
+password. In that case `ZABBIX_USER` and `ZABBIX_PASS` will be ignored.
+
+```sh
+export ZABBIX_TOKEN=othersecrettoken
+```
+
+If you are using custom SSL certificates for NetBox and/or Zabbix, you can set
+the following environment variable to the path of your CA bundle file:
+
+```sh
+export REQUESTS_CA_BUNDLE=/path/to/your/ca-bundle.crt
+```
+
+### NetBox custom fields
+
+Use the following custom fields in NetBox (if you are using config context for
+the template information then the zabbix_template field is not required):
+
+```
+* Type: Integer
+* Name: zabbix_hostid
+* Required: False
+* Default: null
+* Object: dcim > device
+```
+
+```
+* Type: Text
+* Name: zabbix_template
+* Required: False
+* Default: null
+* Object: dcim > device_type
+```
+
+You can make the `zabbix_hostid` field hidden or read-only to prevent human
+intervention.
+
+This is optional and there is a use case for leaving it read-write in the UI to
+manually change the ID. For example to re-run a sync.
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