//ERIC CROES// 

In here, you adding the Summary block, I selected the Grid Style, but you still have 3 more options. Depends what you are looking for. I suggest you to try the 4 options. 

If you want to add the other Blog, you will follow the same process I just did. And once you add a new Blog post, it will appear here. 

In here, you haven't added any BLog post, that's why the error message is displaying. The last option I showed you, is how many Blocg post you would like to display from that BLog to this summar

You can add those blog Pages on the not linked section if you prefer.