You can use the hold command to plot two things to the same figure.
imshow('map_image')
hold on
plot(points_of_interest_x,points_of_interest_y)
You will likely need to modify either the image or the points of interest so that they can be overlaid (e.g. converting latitude and longitude to pixels in each direction).
If you want to label the points in the text file, you can use the text command or the fantastic labelpoints package in the File Exchange.