As per Pilou, draw the circles you want. Note that when you draw them (by entering "(integer)s" or aftewards, in the entity box you can change the number of sides. Use Push pull to pull them up. You pull out the radius, click, then type in the proper radius.
For the horizontal tubes move your view so you are looking at the horizont, choose circle tool. hold it up in the "sky" till you get a red or green circle. hold shift and draw your circle. You can then pull a cylinder that is parallel to the x or y axis. Make it a component.
How to position? I would go to an overhead view and turn on hidden geometry. Move your small cylinder from the top edge up or down until you see z axis (blue) indication and press shift. Move up and down and align the top edge with the top of the fat cylinder (a component) (leave top face on the fat cylinder for now). Then with move tool hover on the top edge of the small cylinder and find the "Midpoint" of that edge. Click down move the cylinder to the top edge of the fat cylinder and hover, then move to the center of the top face of the fat cylinder to find "Center" inference. When the move snaps to that point let go or click. Similarly you can use the edges and points on the cylinders to snap / move the small cylinder down to the midpoint of the fat one.
Use the rotate tool (with option key down for duplicate)to rotate a second component at 60 deg. Get a blue protractor with the rotate tool then press shift. Hover on the top circle edge of the fat cylinder and then move to the center of the top surface to find the center. Then you can click down to establish center of rotation. No need for shift key then, but use option key and rotate a duplicate component at 60 deg.
What is this for. If only for a model or picture that will be viewed as-is. I would not explode the components or affect their geometry. I would not make holes in the cylinder. Instead I select the three components and context menus intersect with selected. this will give the appearance of holes by placing edges in the model. Group these edges for security.
If for some reason you need to make holes. You will have to work inside the components. Holes in the side of cylinders in SU can make messy geometry and also may not look smooth, depending on how many sides they have.
Main things are rotate and move. Learning to use inferences, and constraining movement on an axis.
