You will find the Diaries tab at the bottom of the Seasons window. The tab will appear after you have completely decoded the first chapter of the current Season. Click on a bookmark to expand the list of diaries you can read. Select a picture on the bookmark, and you will go to the required diary.
If you at least partially completed a season when it was active, you will be able to read all the pages of the diary, which you deciphered. If you have not completed the season at all, then only the first few pages will be available for reading.
You can read the diary to the end by purchasing the missing pages. To do this, open the last available page.
Please note: You won’t be able to re-read the current history immediately, some time has to pass after the event has ended.
If you want to re-read the available diaries and the season event hasn't started, just click on Mr. X's Office next to the Manor.