@Ges,
Are you supposed to use the tab "Data_for_JMP" or "Sheet1". I am assuming the "Data_for_JMP" is the right one. I am going to provide step by step instructions on what to do - but I want you to keep in mind and understand, as a community member I wouldn't be offering a solution knowing it is a homework problem. I will only provide advice so you make a fair attempt at solving it on your own. If you share your work, the community will always be glad to help you, but I will not solve the problem for you as the intent is for you to make an attempt on your own using tools at your disposal.
Now, let us go over the attachment, assuming "Data_for_JMP" is the sheet with the data you want ,
Step 1: Import the data into JMP
When you open JMP, navigate to File ==> Open . Select the excel file. This should give you the following interface:
Step 2: Now you have your raw data in JMP from Excel as a data table, open a new script
Step 3: Use the example shown below to delete rows that meet your condition
Clear Log(); Clear Globals();
dt = Current Data Table();
// Assuming you need to delete the "Twymax" in the Cultivars Column
// Select Rows where this condition is satisfied
dt << Select Where(:Cultivars == "Twymax");
// Delete Rows
dt << Delete Rows;
The above acheives what you need. You will need to edit the script I am providing for your conditions. If you have any further trouble, please share your script or your attempts.
Best
Uday