To create runs for a cube plot in Minitab, you select Stat>DOE>Create Factorial Design. On the main screen, you select the Number of Factors (the default is 2--you'll want 3 for the homework) and then click on the Design button. In the Design screen, select the design you want from the options listed (you'll want Full Factorial). After entering your choices and returning to the main screen, click Options. It's convenient to have randomized runs when designing an experiment but inconvenient when entering data for homework--click on Randomize Run Order to remove this option.
After returning to the main screen, you may want to click Factors in order to change the factor names (under the Name column) and levels (under the Low and High columns) to something that is more user-friendly. For Problem 1 in HW 1, the factors are already labeled A, B, and C and would not need to be changed. The factor levels, though could be changed from -1 and 1 to S and M, respectively (you will need to change factor type from Numeric to Text). Click OK and your worksheet will have all the run levels entered and labeled. You can enter your responses in an adjacent empty column (this will be C8 for HW 1 Problem 1)--be sure to name the response column.
With your response column entered, you are now ready to construct a cube plot. Select Stat>DOE>Factorial Plots, check Cube and then click on Setup. In the Setup window, double click on each of the three factors in the Available window, so that they appear in the Selected window. Click in the Response windows and then double click on your response column--it will be listed in the Response window. Click OK in the Setup window and click OK in the main window. Your cube plot should appear as a separate graph window.
HW 1 Problem 2 note: For this problem, you need to compute your responses, i.e., measures of location and spread. To do this, first enter the replications from the 8 runs in 5 separate columns (C1-C5) in a separate worksheet (create a new worksheet by selecting File>New then selecting Worksheet). If the data were out of order, you would need to make sure that the order in which you enter the data from the 8 runs is consistent with the row order that Minitab creates for its factorial design. After entering the data, select Calc>Row Statistics, click on (e.g.) the Standard Deviation button, click in the Input Variables window, select C1-C5 as the input columns, then click in the Store Results In and type in C6. Repeat this exercise using different storage columns for the remaining statistics. Now create a third worksheet for your factorial design, just as you did for HW 1 Problem 1, but with factor names and levels appropriate for HW 1 Problem 2. The columns from your second worksheet containing summary statistics can then be cut-and-pasted into the third worksheet to form the response columns for cube plots.
As an alternative to the above approach for Problem 2, the procedure can be collapsed in a single worksheet. Generate the design first, then enter your 5 columns of data in the open columns of that worksheet, compute the row statistics and save them in adjacent columns. From there, you are ready to create your cube plots.