Short answer
Press ⌃⇧⌘4 to capture an area to your clipboard, then press ⌃⇧⌘U. Aktar uploads the screenshot and copies its link, ready to paste.
Holding Control with the usual macOS screenshot shortcuts (⌃⇧⌘3 for the whole screen, ⌃⇧⌘4 for an area) copies the screenshot to the clipboard instead of saving a file. Aktar's global shortcut uploads clipboard images as PNG files.
If you prefer saved screenshots, drag the file onto the menu bar panel, or copy it in Finder and press ⌃⇧⌘U.
Tip: set the output format to Markdown to paste screenshots straight into GitHub issues, pull requests, docs or notes.