Release Procedure for PO

Dear Experts ,

I want all the Pos created with document type NB for a plant 4100 to be

1. created by the purchase clerk

2.then released by purchase officer

3. Finally released by purchase manager

For this i created characteristic

then created a class (type 032) & assigned this characteristic to it .

created a release group z1

created 2 release code 00 & 01 with group z1.

created a release indicator C , with released tick box .

then defined a release strategy ST with rel grp z1& assigned release code 00 & 01 to it .

what do i do now ?

the release strategy is not working

no release tab is shown in pos

pls guide

Regards

Anis