Email

Adding an additional email account is straightforward:

Add an email account to your iPhone, iPad or iPod touch – Apple Support

However, if your aim is to create a second user-profile - that allows two users to independently use the device, similar to a PC or Mac computer - then you are out of luck. Outside of Educational environments, iPad (and iPhone) are principally intended to be single-user devices.

I'm not entirely clear on what you want to do.

Do you want to read that person's email? You can add an email account by address and password in Settings > Mail > Accounts.

Do you want to allow them to use your iPad as a separate user? That is not supported.