Login via winbox, on the left, click "Queues"
You should get the "Queue List" window:
Click the "+" button to add a queue:
You'll now get the "New Simple Queue" window:
Where is says "target", select the interface that you want to apply the bandwidth limitation to from the drop down, on the "Target upload" and "Target download" entries, put in the values that you want. Once you have done that, on the top, click the "Advanced" tab:
On the "Limit At" "Target upload" and "Target download" entries, put in the same values that you specified in the previous tab and then click "Ok" on the right top of the window.
Do this for all the interfaces that you'd like to apply limitations to.
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