Choose Home tab→Select group→Select.
Do one of the following:
To select one element, click it.
To select more than one element hold the Shift or Ctrl key and click each element.
To select more than one element at once, drag a box around the objects.
To select one of several overlapping elements, use QuickPick.
To select elements with similar attributes, use SmartSelect.
Tip:
You can use the Polygon Fence option on the Select command bar to draw a polygon fence around elements in the Draft environment.
QuickPick helps you to select elements that overlap each other.
Position the cursor over the element you want to select and stop moving the cursor.
When the cursor changes to the QuickPick prompt, click. The software displays the QuickPick list near the cursor, with an entry for each selectable element.
Move the cursor over the QuickPick entries, without clicking, to highlight the corresponding elements.
When the element you want to select is highlighted, click the corresponding entry on the QuickPick list.
On the Select command bar, click the SmartSelect command 
.
Click the element you want to select.
For example, if you want to create a selection set containing blue lines, click on a blue line.
Once you create a selection set, you can use the Properties command to make changes to the elements in the set. For example, you can use SmartSelect to automatically scale similar text elements.
Do one of the following:
Double-click in free space.
Select another element without holding the Shift or Ctrl key.
To clear the selection of one element and leave other elements selected, click the element while holding the Shift key.
Tip:
You can use the QuickPick Options dialog box to specify the QuickPick properties you want. For example, you can specify whether the left or right mouse button activates QuickPick.
The QuickPick prompt (A) indicates which mouse button you should click to activate QuckPick.
You can change the element highlight and selection colors with the Solid Edge Options command on the Applications menu.
In synchronous part and assembly documents, you can also use the Selection options adjacent to the Select command to control how elements are selected.
Construct an extruded protrusion or cutout using the Select tool
Construct a revolved protrusion or cutout using the Select tool