Adding Email Addresses

We are implementing a new performance management tool from a third party. We are pulling all the data for this tool from E1. We currently don't have any of our employee's emaill addresses associated to the employee in E1. How or where would be the best place to add email addresses to our employees?

In addition to email addresses, we need to have three fields that don't exist; 2 for percentages unique to employees and one for alternate supervisor. We originally thought to use the payroll category codes 11-20 but are unsure if there are any other possible options to add this data.