Step 1: go to https://www.tzima.gr
Step 2: Find the classroom you are hosting in the TZIMA ONLINE menu
Step 3: Select the classroom from the menu
Short video follows.. (you might have to right click on the video to show controls in order to press play.)
Step 4: You sign in with your username and password
Step 5: You join or Start room by clicking on the bar.
You now must successfully complete the login procedure.
Tip: if you would like to login faster you could start class with Listen only and later within the classroom enable your Microphone.