I assume your data with the log return values, or the values you will calculate them from, is in some sort of file, for example a .xlsx spreadsheet, or a .csv text file.
So you must first get that data into the Matlab workspace. Matlab provides alot of data import functions. A good starting point would be to check the documentation for readtable, and readtimetable. Just type doc readtable, or doc readtimetable on the command line and it will bring up the documenations.
Depending upon whether you have exactly what you want already in the table you may have to do some mathematical manipulation of the variables that you've assigned to caclulate the quantitites you want. I assume you know a little bit about doing basic math with MATLAB, but if not I suggest first completing the MATLAB On Ramp training (takes a couple of hours). https://www.mathworks.com/learn/tutorials/matlab-onramp.html
Finally once you get to the point that you have assigned some data you can plot it using the plot command. So, if for example, the times and values for the first and second asset respectively were now given by t1 and logReturn1 , and t2, logReturn2, (names are arbitrary, whatever you've assigned in your code), you could plot them with
Again, you can type doc plot on the command line to get documentation on the plot command.
After you've gone through all of the above, and you have written some code, if you are still stuck (errors that you can't understand or whatever) please attach your code, using the code button on the MATLAB answers toolbar, and copy and paste the errors you are getting, and ask for further assistance.