Install /plum/ to import keymaps and input methods. Go to the command line and type
curl -fsSL https://raw.githubusercontent.com/rime/plum/master/rime-install | bash
To install the rime-avestan package, cd into the directory where the plum installation is located and type bash rime-install a-pontifex/rime-avestan
On Windows:
Switch to Rime as your keyboard layout.
Right-click the icon that either says A or 中 and click '輸入法設定(S)'.
Click the button 獲取更多輸入方案 on the bottom-left corner of the dialog box, which will redirect you to the inbuilt plum command line.
Type a-pontifex/rime-avestan into the command-line.
Close the command line window after it finishes installing the package.
Select Avestan Input in the dialogue box.
Selecting rime-avestan as your input method
press Control-grave on your keyboard, use your arrow keys to select 'Avestan Input' and press enter to switch to Avestan.
Press shift to alternate between Avestan and ASCII.