scroll down through these screen captures and follow along - there are 11 steps

1) Tap Settings then tap Mail, Contact, Calendars

2) tap on the account to modify (your display may only have one account)

3) your account details display; scroll down to Advanced

4) tap Advanced

5) tap Authentication (your display may be blank after the word Authentication)

6) tap Password then tap the Advanced button on the upper left then tap the account name on the upper left

7) Tap Account then scroll down then tap SMTP

8) tap your primary server (probably the top entry)

9) tap Authentication (your display may be blank after the word Authentication)

10) tap Password then tap the server name on the top left then tap Done on the top right

11) tap the server name on the top left then tap Done on the top right
You should now see a "Verifying" message then your list of email accounts (or your one account) should display and you're done.