After you have linked to OneRewards, you have to enable OneRewards at terminal settings to use member feature.
To enable OneRewards, click on the Master Data icon > Terminal.
Then click on Terminal Settings.
Click on Edit.
Click into "Document" tab.
Scroll down to find OneRewards, and check on checkbox for "Enable OneRewards", then click on Save.
**Make sure to synchronize after committed the changes.
Frontend
Login frontend.
Your member tab will be enabled.
Click on the member tab and you can find member at here. Click on Search and choose your member.
You can now proceed to create transaction with member.