While logging into the Customer Center ,using the Standard Customer Center role ,there is no link to Enter Sales Order.
Solution:
By default, the Customer Center has Permissions > Transactions > Sales Order = Edit. This lets users Create or Edit an existing Sales Order that they have created.
1. Navigate to the Item that you want to be displayed on your Customer Center or Web store.
2. Click on the Web Store tab > Display in Web Store = T.
3. As Administrator navigate to Setup > Company > Enable Features > Web Presence and under Access put a check mark on Online Ordering.
Then the option will be displayed in the customer Center as shown below:
