Code for changing the size of the footer block (background) and font size

I am using woocommerce and the shoptimizer theme.

I want to change the height of my footer background, the font size and the background hover colour (When pointer is over the link). Is there some code that I can add in order to do this? How do I add the code.

I understand CSS but am not sure what is needed for this. (font-size, height etc)

I have tried a two plugins but they throw out critical errors.