Using following steps you can add your own custom logo in footer.

1. Step 1 : Hide the footer logo 

Add this CSS code to location given:

wp admin panel -> Plugins->Editor->WPLMS Customizer Plugin -> Custom.css

OR
Wp Admin->Appearance->Customize->Custom CSS

Code:

#footerlogo{
display:none;
}


2. Step 2 : Upload the Logo in WP Media

3. Step 3 : Add the logo in the WPLMS Options panel -> Footer -> Copyright Section.

Refer below video on how to do this :