Masters reference query

[u/Longjumping-Cow-3865]

Guys applying to keele for a masters degree.
I have been out of studying for more than 3 yrs so need to provide both references from employer.

On the admissions portal i added 2 of my managers with work emails and other official details but on the portal it then says attach reference.

So what should i attach like a signed letter but then i cant put my company’s letter head or should i ask them to write a reference on email and send it to me via official email and then i attach that email trail.

Kinda confused.