The lasso can be a bit tricky. You can just drag and draw around the edge, but that’s not very precise. There is a precise method. When I had Photoshop, the precision method was to mouse over where you want to begin; then, while holding the option key, click at the start, mouse to the next position and click, and repeat until you’ve “drawn” the lasso around the section you wish to isolate.
The lasso can be a bit tricky. You can just drag and draw around the edge, but that’s not very precise. There is a precise method. When I had Photoshop, the precision method was to mouse over where you want to begin; then, while holding the option key, click at the start, mouse to the next position and click, and repeat until you’ve “drawn” the lasso around the section you wish to isolate.