You really need someone who uses btopenworld, but in the meantime there is some help on www.btopenworld.net/ if you type emailsubaccount into the searchbox.
A subaccount might be ok for what you want. ====================== Go to My Account (for your security, you may need to re-enter your password). Click Manage sub-accounts. You'll see how many you've created and how many more you can create. Scroll down and select Create a new sub-account. (If the button isn't there, it means you have already reached your maximum number of sub-accounts.) Enter your chosen username, password and add details of whoever will be using the account. Click Create sub-account. ======================
Depending on your circumstances you might want to change the password on the primary account as it will still work and using it would almost certainly allow access to the subaccount.