Adding another site to Word press

We had a designer organise a new website for us through Word Press and really liked the results and now want to add another website for our side business to Word press.

I’m going to organise this site as it is a very simple website that we require but I wanted advice on how to link the two together i.e – can we organise it through the same administration page, or do I need to set up a new account with WordPress?

I am relatively new to word press but have used similar programmes in the past and really just want to connect the two websites together and update the new one so it is in keeping with the word press style.

Many thanks

Abbie