Ok,
I’ll try not to scare you. 
Assuming you already have an item that is displaying the current temperature.
You will need to store historical temperature information, so we can actually know what the temperature was 1h ago.
This is called “persistence”.
This is explained here: http://docs.openhab.org/configuration/persistence.html
If you have no preference in which database to use, I recommend InfluxDB. There is a nice tutorial here.
After you have successfully set up persistence, you need to think about how to visualize this.
Also here you have many options. But on this forum, I think Grafana is used in many (most?) cases. This is also explained in that tutorial.
Good luck!