Maybe you need to add a link to any external website or any existing blog that related to your business. Now, to add the new external link as the Menu in the header of your Online Store,
1. Go to wordpress Menu > Appearance > Menus
2. On the left panel, select the “Custom Link” tab
3. Insert the information accordingly. Then, click the button “Add to Menu”
4. You should see your newly add menu, in the menu listing
5. Next, click the button “Save Menu”
6. Go to your Online Store web, and you should see the menu Blog is there.