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Scroll down to the bottom of the page, and click on the lock icon, or select "Permissions / Change Password" from the dropdown menu.
To allow this person to access the system, select "Yes" under the "Account Enabled?" section.
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Account Impersonation can be set through the "Must be impersonated?" option. This is mainly for shared supervisor / administration accounts that have special auditing requirements - for most accounts, this should be set to "No". For more information about this option, see the Impersonating Accounts page.
To provide the user with a password, you can have the system generate a random password for you by ticking the box shown below, or you can specify a password by typing it in the "Set new password" field. In both cases, the new password will be emailed to the user automatically.