If you have a Third Party MILogin account and access to MiEHDWIS, and will be using do official business with the same email/account for each water supply on behalf of multiple water supplies, you already have the ability to upload data for any systems you oversee. You just need to choose the correct entity when creating a new work item.
If you will be using a different do official business with a unique email/account for another system on behalf of each water supply, you would need to create an additional Third Party MILogin account for each supply, request access to MiEHDWIS, and then be approved by a MiEHDWIS System Administrator.
...