I will presume you already know how to write insert as select so that you can insert data from one table to another.
That said, the only difficult part of your request is getting data form the excel spreadsheet. The reality is there is no simple way to do this. You must do one of:
1) export you excel sheet to a CSV file, then define an external table to the file
2) buy a third party excel mapper product (if you can find it, and it won’t be cheap), that provides an api from oracle PLSQL that allows you to manipuate excel files directly. Good luck with that one.
3) check oracle for a utility or api that does same as #2. I seem to recall that had such a product at one point but do not remember its name. Maybe a tar put to metalink can get you that answer.
#1 above is the most common way people do it. This fact should tell you something.
Given #1 above, once you have defined the external table, you can query it for data directly so you do not actualy have to load it anywhere unless you want a record of it for historical purposes, or you need to update the data. The point here of course is that the excel data is not directly available via the XLS file.
Good luck, Kevin