[HELP] Mikrotik CRS109 Segmentation Questions

Networking newb here...
I have a mikrotik CRS109-8G-1S-2HnD-IN that I would like to segment.
Basically I am putting this in my parents' small retail setting where the terminals and office need to be on separate networks on the same router. There is only 1 internet source and I am hoping I can segment this router so that I have different IP schemes on each of the ports so that the two sides of the network can both have internet but not be able to see each other.
Right now I have port 1 set up as the internet port. Port 2 is set up with a 192.168.2.xxx scheme and port 3 is set up with a 192.168.3.xxx scheme. Both sets of computers are getting internet connection, however, the problem is that the 2 scheme terminals can ping the 3 scheme office computers and vice versa. I really need to get this segmented so that there is no crosstalk across the ports.
How can I accomplish this?
Any help will be greatly appreciated