The saying of "You can't make silk purses out of sow's ears" means that you cannot make something look good that is already ugly.
"You can't make silk purses out of sow's ears" can also mean that you cannot take something of little value and make it into something more valuable.
For example if you have an old car that is really in bad shape that is of little value then you may not be able to make that car into a more valuable car no matter how much work or money you put into it.
It's a pretty old saying to mean that something ugly or inferior cannot be made into something good, lovely, of value etc.
Or if you have an ugly dress and you're unable to make the dress into a fancy nice looking dress then someone might say to you that with that dress you can't make silk purses out of sow's ears.
Silk Purses are nice but Sow's ears are not.