I'm going to assume you can already print from the computer to the Zebra. I am also going to assume that since you have Excel, you also have Word. The first thing you need to do is layout the labels in Word. I cannot be more specific because I have no idea what size labels you are using.
Create and print labels
Next you need to merge the values from Excel into Word
Mail merge using an Excel spreadsheet
Here are some videos that might help
Mail merge Word
Calibrate the media sensors by power cycling the printer.
If that does not fix the issue you can adjust the sensors using the following procedure.
In the menu go to advanced setup 3 and enter password (default 1234)
Select MEDIA/RIBBON CALIBRATE
Follow onscreen prompts
If this does not fix the issue you may have a bad media sensor.
ZEBRA G77752M KIT OPTICAL MEDIA SENSOR Z4M Refurbished
or Main board (I'd recommend getting a part number from the main logic board and ordering by that number as there are a number of different main logics for that printer that are not interchangeable.)
MRP provides IT Parts Product Supplies and Services
Ethernet cable Must be plugged in and the printer must be ready for about 60 seconds before you enter the menu or the Ethernet settings will not show up.
Zebra printers are not really made to print PDF files, if the only option is PDF I'd recommend switching to print on a laser. Also open the PDF and see if they are correct in the original doc
