Like everything in JMP there may be more than one way to accomplish your goal. You did not specify which JMP version you are using because it has changed somewhat in more recent versions. You can set up your experiment and in the user specified increase the number of runs to equal the number of runs that would equal the number of replicates that you desire. So for example a 4 continuous factor example generated a 16 run default and in the user specified field I entered 16X5 = 80 and obtained 5 replicates of each setting. Alternatively you could generate the 16 runs and then clone those 16 runs 4 additional times and randomize with and additional column using the column formula= random function.