For a single object, you can left click on the object, (it turns yellow) and with the mouse button still held down, drag it around.
To move more than one object around together, press the Control key first and then left click on each object that you want to move as a group (holding down the control key all the time).
Then at the last object, drag to move all the selected objects around together. If you release the Control key at any time, the objects will not move as a group.
Another way is to Hold down shift, draw a box around the models to move, then let go of shift, and hold down alt, then move the group of models.
Select a group of objects, right click and select Align (top, bottom etc) to align the selected objects. Which object should they all align to ?
The object you selected first i.e. which will have the blue dots is the key object that others will align to.
When selecting a group, you can press shift, a box opens and you can drag the mouse around the objects to select the group to align.
There is no Undo for this action of dragging and setting alignment.