Will there be more parts to this story, such as 3, 4 and 5 or just the two? If so, there are some change that you can make to things that will make it a little easier for people to get to things in order.
If there are just going to be a few parts to this story, what you can do is to change the published date on the posts so that they will appear in the correct order. This support document explains how to change the date or time.
If there will be many in this series, or if you are going to have several series, you might want to take a look at this support document.
You can keep the series' separated by making categories for each series. Also with the theme you are using you can put categories in the top menu by utilizing the custom menu feature and then you can put the different parts under that category as children. You might also want to include a link at the bottom of each part to the next part, or perhaps to all parts.