Log into your exchange account from the web using Outlook Web Access (OWA) from a browser as shown below. You want to use the URL that takes you directly to the login page without any other login steps.
Next log into your exchange account
Enter you user name (without the domain) as shown below. If successful this will be the user name and password to use in eTask.
Once you login you will see the default "Light" version of OWA unless you used Internet Explorer. Note the URL might change but use the one from the previous step above.
Setting the Exchange account information in eTask
Fill out the account information to include the URL you used above, username and password. Next press the "Test & Browse" button as shown below (iPad). The iPhone view is very similar.
If all the information was entered correctly you will see a list of Task folders from your exchange account. Unless you have changed the default task folder name it will show as "Tasks" as shown below. Press the line with the long number and the folder name, Tasks in this case, will be shown in the selected window. From here press Save and Save again.