Choose IP and ENI > ENI in the left sidebar to go to the ENI list page.
Click the ID of the desired instance to enter its details page.
Click IPv4 Address Management in the tab to check existing private IPs.
Click Bind in the Bound Public IP column.
In the page that appears:
Select the desired EIP and click OK.
If no EIP is available, click Create at the top of the pop-up box to apply for one. For more information, refer to Applying for EIPs. After your application is approved, return to the page and click Refresh. You should see the EIP you applied for. Select it and click OK.