Email problems on ipad
This is known as Phishing or Social Engineering.

You were tricked into giving away your login details, by being directed to a site that looked familiar, but which wasn't actually the legitimate site you thought it was.

You were correct to immediately change your password. In most situations this is sufficient to prevent further access by the phishers.  They don't really want to go to any effort to spread their spam, fooling you once would be enough; trying to hack you after you changed the password would be too much like hard work.

It is very unlikely that any malware is on your iPad - but it may 'remember' the fake site in your history, so be careful when going to the legitimate site that you do indeed have the right one.

If you normally use password auto-fill on your iPad, then one very good sign of a fake site is that the iPad will not offer to auto-fill. As far as it's concerned it's not the same site. It is far more likely to notice the difference between yahoo.com &amp; yalhoo.com etc than a human.

See Jaime Santa Cruz's answer for further practical advice.