Add Device to Zabbix

Zabbix agent

Access to the device terminal and install zabbix agent apt-get install zabbix-agent for Debian bases systems.
Configure the agent, the file on Linux is at /etc/zabbix/zabbix_agentd.conf, on this file change Server to the zabbix server ip, right now 10.20.0.2.
Now start the zabbbix agent with sudo systemctl enable --now zabbix-agent and restart it with sudo systemctl restart zabbix-agent or the equivalent commands on your machine.
Now on the zabbix web interface found at sentinel.arditi.pt click on monitoring and then hosts and after that click on the button Create Host on top right corner.
Now on Host Name input your machines ip address or DNS name, on Visible Name input the name of the machine or something similar, on templates select the template that is closer to your machine and that says by zabbix agent, for example on a linux machine we would use Linux by Zabbix Agent, on host group select the most appropriate group then on interfaces click on add and select agent, now on agent ip address put your machine ip and on DNS name put the machine DNS name if it has one, after inputing all of that information click on the add button on the bottom of the popup page.

Check if your device has snmp and how to turn it on, most common is on the web interfaces of the devices, check also if the snmp version is v2 or v3, if it has v3 use that version.
Check on the snmp for its snmp community key, by default public, on snmp v3 search for security name, authentication protocol and its passphrase, search also for privacy protocol and privacy passphrase, if none of this is defined define it yourself.
Now on Host Name input your machines ip address or DNS name, on Visible Name input the name of the machine or something similar, on templates select the template that is closer to your machine and that says by snmp, for example on a linux machine we would use Linux by SNMP, on host group select the most appropriate group then on interfaces click on add and select SNMP, on ip address put the machines ip and on dns name puts its name if it has one.
On SNMP version select the one your device has for snmp v2 on the top click on Macros and then on Inherited and host macros, there change effective value for snmp_community for the value it has on your device, for snmp v3 put the security name of your device, on security level authPriv, on the authentication protocol select SHA1 and on passphrase put the one that shows on your device, on privacy protocol put AES128 and its passphrase, after inputing all information click add on the bottom of the page.

To add a trigger you need to first have a correspondent item to it, on zabbix web interface click on your host and then click on items
Click on the button add item on top of the page, put its name select its type, if its for a zabbix agent host select it and if it is for snmp host select it, on key type a unique name for that item and on type of information select the most appropriate one.
If its an snmp agent you need the specific OID for an item, for example for seeing the temperature of a device its a specific OID, you can check that on the manufacturers manual or on the machine.
After inputing all that click on add.
On top click on triggers and click Create Trigger, input a name for the trigger, its severity,then on problem expression click on add, select the item you want the trigger and set a result for the trigger to activate.
On OK event generation click on Recovery expression, then click add, select the same item as used on the last step and set a result acceptable for the problem being solved, then click on the add button on the bottom of the page.
To edit these values just access the triggers or items after being created and change the values there.