How to add new block into Purity III - Magazine layout?

I'v installed Purity III and then, check update T3 to: T3 v2.4.1
That's great.
Default magazine layout:


Right now, I want to custom on magazine layout (eg)
Add two blocks: myblock1, myblock2 above mainbody.


I read documents on T3-Framework, but can't fix a problem. I hope I give you my step-by-step you will support me.

Step 1: Create two postions in TemplateDetail.xml file (Purity III - templates)
...
myblock1
myblock2
...
Step 2: Add new module position into one-sidebar-right.php file
...











....
....
Step 3: Add somes position for testing into myblock1, myblock2
Front-end: It's so good
Unfortunately
Back-end: myblock1, myblock2 doesn't show in magazine layout.

Please, give me some solutions. I want to manage theses blocks in back-end.

Thanks