Drag and drop accounts you follow on the right side, to lists you have created on the left side.

There are a couple of things to help you out:

• You can select multiple items by using shift+click or ⌘/ctrl+click
• If the colors are too hard on your eyes you can change them on the Settings page.
• If you have multiple accounts selected, you can batch add/remove them from a list.
• You can unfollow an account by dragging and dropping it to the unfollow button on the left side. This doesn't work with multiple accounts selected.
• There is some basic keyboard navigation using the arrow keys or h/j.
• You can edit a list title by clicking the ⁝ icon next to the list name.
• You can delete a list by clicking the ⌫ icon next to the list name.
• You can filter the accounts you follow using the search bar at the top.
• You can sort the accounts you follow using the button at the top.

If you find any issues you can report them on the Github page.