Open the Day Schedule panel (D on desktop). Drag a task from the list onto a time slot to block it. Resize by dragging the edge. Delete by dragging back out.
Google Calendar sync — Settings → Integrations → Connect Google Calendar. Blocks push to your calendar (green = LemTask origin). Existing Google events pull in (blue = calendar origin) so you don't double-book.
Why time-block? Estimating time forces honesty about what you can actually fit in a day. Most people cut their to-do list in half within a week.