You can add your agent credentials to your Partner account to be able to submit CIS returns and automatically verify subcontractors on all your CIS client accounts.
Login to your Partner account and navigate to Settings > Organisation > Details & Tax.
Click on the Tax tab and fill in the HMRC sender ID and password (your agent services account credentials).
Once you have added your details, these will be used on all client accounts when performing automatic subcontractor verification.
Please note: you can skip steps 1 & 2 on the auto verification guide (linked above) as these steps apply to business customers only.