Maybe you can try with beta release.
So your data should be in the first sheet of your excel file.
In collector, you have to create your collection and your fields.
Then in the items tab, there is a new bottom "import an excel file"
Then you upload your file. It will appear in the list. Select it and then a preview of the 10 first rows will appear.
under the preview, fill the first row of your datas ("2" if the row 1 is the title column for example)
And for each field of your collection, fill the letter column of the data in your file (i hope you have less than 26 columns because it doesn't work for more than 26 columns for the moment)
When it's done, click on "submit". A popup opens and click on the other "submit". You will see "import en cours" and the number of imported items that will increase.
At the end you will see "import terminé" and the number of imported items will stop.
By default the items are unpublished. If you want them published by default, modify the file /administrator/components/com_collector/controllers/import.raw.php at the line 364 add '$table->state=1;'
Tell me if it works
