understanding a used filter

[clc]

I picked up a used Doughboy Silica 1 model 17400 w/ pool power pak1 pump at a garage sale -( I know - buyer beware - but the pump works and it's this or I dont open the pool at all this summer).
I expected to find owners manual online but not for this older model
looks easy enough to figure out BUT , labeled ports are 'to pool', 'to pump' and 'to waste' - i dont see a switch /valve to flip between -
there is a propeller shaped gizmo on the top of the device, which must be involved in the control -
i expect to refill w/ 100# silica sand andfire it up!
anyone familiar with this old model?

any help is appreciated