Often the best way to learn is by doing and dragon runes are no different, this method should hopefully have you able to read in a week or so depending on how often you practice. I used this alone however I would recommend checking out the lessons page here on Thuum.org if you haven't already.
Step 1: First off, you're going to need a letter key. There is one here in the lessons page https://www.thuum.org/learn/grammar/alphabet.php and another on uesp wiki titled "dragon alphabet". Either keep this open in one tab, print it out or write it down so you can easily access it.
Step 2: Second you need something to read. The uesp wiki records all of Skyrim's word walls in runic, romanized and translated Dovahzul. Search for "Skyrim shouts" and click on the uesp page. (Or copy and paste this https://en.uesp.net/wiki/Skyrim:Dragon_Shouts) From here you can select the individual shouts to see their word walls.