Step 1:

Navigate to WHMCS installation folder > templates > hostiko > layouts.

Step 2:

In layouts folder select the Hostiko WHMCS Template you are using on your site. as shown in screenshot we are using layout 89 so we will select the wp-89 folder.

Step 3:

In your layout folder navigate to assets folder.

Step 4: 

In assets folder navigate to images folder.

Step 5:

Now, navigate to your logo file on your computer in left side window and right-click on it and select Rename.

Step 6:

Now rename your logo to footer-logo89.png. If your logo is in a Jpeg format then convert it to png and then rename it.

Note:  rename the logo according to the layout you are using. In our case we are using layout 89 that is why the name is footer-logo89.png.