These terms are similar but not the same. To enumerate means to list, usually giving a number or a letter to distinguish each item in the list. You might do this when you wish to list the issues you wish to address in your text. Or to give list of reasons or causes. The numbering is for ease of reference and doesn't necessarily imply order of importance.
Sequencing means placing items in an ordered list. Items higher in the list must occur before items which are lower down. You use sequencing when you describe a process. In a process the ordering is important; you can't make a cup of tea until the water has boiled, for example.
The example below contains two examples of enumeration. By mousing over the text you can see how the author handles this text pattern and you can see an explanation of both examples. Before you do that you should also mouse over the title to see a further explanation of enumeration.
You can see an explanation of enumeration by mousing over "Enumeration" at the top of the article.