Showing character using concrete details adds texture to the storytelling.
Here is an example.
Meyer Wolfhseim is the sort of person who boasts wearing human molars for cuff links. <said by his neighbour Darla>
or
Meyer Wolfhseim is the sort of person who wears a woolen coat on a sunny day.
Keeping the above example in mind, here is an exercise.
Write 5 sentences about a character from your WIP.
<Name> is the sort of person who…
Against each of those five descriptions, think about who might say that (and if you want, when).
Repeat for another character. You can pick protagonist / antagonist or any other characters from your WIP. Remember to include concrete details.
Here is a great video that gives three practical tips to create characters. Regardless it is for art, the principles apply for writing too!