How do you edit the size of pictures in blog?

I realised that blog on square space don't allow you to insert a picture and edit its size like wordpress or other documents eg microsoft. I insert a picture in my blog but it's so big! They only allow you to adjust to postcard, stack and what not. If it is a blog, I would prefer my pictures to be in line with my content, pin it to the left for example and my words can do a wrap text around it. The image is to big. The blog is not flexible.
Does anyone have the same issue? Is there a way to fix this?