OK, let me see if I understand what you are wanting to do.
In your router, you will have a WAN connection to your ISP that will have 6 PPPOE accounts encapsulated in it. You want the router to split the 6 PPPOE accounts so that each account is routed to a specific VLAN on an 802.1q trunk to a RB260GS switch that will split the VLANs out to various physical LANs. The result is that each LAN port on the switch will connect to the internet via a different PPPOE account. Assuming I am right, you don't have enough ports on a RG260GS to use all 6 PPPOE accounts as a separate LAN from the switch, but there are ways around that.
Since you are asking about this in the Switch OS section of the forum, I have to assume you are looking for the switch configuration, rather than the router configuration. Easiest answer is to take a look at:
http://wiki.mikrotik.com/wiki/SwOS/Router-On-A-Stick
That pretty well covers what you are trying to do in the switch. Note that the examples start with the RB250, but they also explain the differences in the RB260. As I have never needed to deal with PPPOE, I can't help you with the Router configuration part of it.
Did that help?