Here the sleeve is just started onto the seal surface. Note that the flanged end goes on the shaft first, as it will be used to push (pull) the fragile sleeve into position. If the groove in the housing is substantial (chances are it will not be too big), it is advised to fill the groove with a structural cement, something like JB Weld for a filler. It is also advised to apply a little sealant to the joint between the housing and the sleeve to prevent internal leakage after installation. I used a bit of blue silicone sealant.