I have a Mikrotik router that is connected to the Internet by PPPoE connection providing it 6mbps. It provides multiple clients in 192.168.1.0/24 subnet IP leases by DHCP. I would like an easy way to limit each IP leased in that subnet too 2 mbps so a single client does not max out the circuit. How is that done?

The problem with doing that is when the connection is quiet, all clients still only get 2Mb.
You could look at doing something like this to ensure a fair service to all, it creates a queue called default-sfq (as my OCD doesn't allow a hotspot or wireless queue on the WAN), target could be your PPPoE interface or you could specify your /24 with destination 0.0.0.0, max-limit is download/upload.

IF the connection is at full utilisation this gives a round robin approach to packets.

Can you explain how this works a little more? If this works it would be wonderful. Basically we run into issues when the connection is maxed by one user when anyone else wants to use it they say its slow as mud. What is significance of the "max-limit=55M/15M"?

I tried this:

/queue simple
add disabled=yes max-limit=256k/1M queue=pcq-upload-default/pcq-download-default target=192.168.1.0/24

But it seems to pool all the IP's together and limit them too 1mbps. I want each IP separately limited too 1mbps.

lets say your provider upload speed=1Mbps and download=10Mbps. your subnet is 192.168.1.0/24.
you want every user to have 256kbps upload and 2mbps download

/queue simple
add disabled=no max-limit=1M/10M queue=pcq-upload-default/pcq-download-default target=192.168.1.0/24

you have to set UPLOAD/DOWNLOAD rates to pcq queues. see the photo below...
disable also FASTTRACK rule in firewall-filter if exists.