After a one day brake here comes the lesson 3 appendix, the lesson which will finish all of Hiragana and Katakana once and for all. And it's not gonna be all that hard either - you already know most of it. There are just a couple of points I'd like to make in order to finish with everything, and all of them are really simple.
1. Double consonants
Some words in Japanese, such as kekkon (marriage), have a double consonant in one or more places. In order to double a consonant in kana, all you have to do is add a little tsu (Hiragana - つ, Katakana - ツ) in place of the first consonant. So kekkon in Hiragana will be written like this - けっこん. The height of the little tsu is about half of that of the normal one.
2. Long Vowels
Long vowels in Japanese are about 1.5 times longer than that of normal ones.
Getting long vowels in Hiragana is simple - just put the same vowel one more time after a syllable ending with that vowel, or the vowel itself - ああ (aa), さあ (saa), いい (ii), うう (uu), etc. However, え (e) and お (o) could be doubled by either using the same vowel, or by using い (i) or う (u). So both ええ(ee) and えい (ei) are read "ee", and both おお (oo) and おう (ou) are read as "oo".
Getting long vowels in Katakana, however, is ..... even simpler. No need to remember anything here, all you have to do is add a line after the vowel to make it long.: アー (aa), イー (ii), ウー (uu), エー (ee), オー (oo).
Just a little remark about Japanese punctuation. The Japanese full stop is written as a little empty circle instread of a dot. It looks like that - " 。". Also, all the sentences in Japanese end with full stop, even the questions - there is no question mark in Japanese. Lastly, the comma in Japanese is inverted for some silly reason - instead of written from right to left like in English and pretty much every other language ( , ) it is written from left to right ( 、).
Congratulations! Now you know everything you need to know to start writing in Hiragana and Katakana. From the next lesson on, we'll be studying grammar!