There is no difference, visually, between tubes and regular graphics.  It's just that they have a transparent background and are promated to a layer.  Tubes are file hogs and aren't really neccessary.  If you just want to use them because they have a transparent background and a layer, you can just save them as is with a psp file extension.  Just click on "File / Save As" and click on the drop down arrow in the 'save as type' area and put PSP there.   But that's also a large file.  I just save them as jpg's because it takes just a second to make a background transparent and to promote it to a layer.  That way you don't have a lot of large psp files or tubes and can make a tube in a second if you want it out of any graphic.
 
But if you really want tubes, you can make a seperate tube folder in your C drive or wherever...out of PSP.  Meaning don't save many tubes to the psp tube folder in the program files. Reason being is because psp will take too long to load if many are stored there.  Same thing goes with filters you save.  Then you can categorize your tubes with sub folders. 

To make PSP recognize them in your new folder, click on "File / Preferences / File Locations". 
Click on the tubes tab. 
The first 'slot' will be filled in with the default location. 
In the second slot, click on the browse button and browse to the new folder you put your tubes in and highlight the folder and click OK. 
Now it will be in the second slot. 
Make sure 'enable path' and 'use subfolders' is checked below this slot.
And if you want all tubes to now be saved to this new tube folder, make sure "Save to path" is checked under this second slot, and not the default one. 
Now OK that box too. 
You may have to re-start PSP for it to take effect. 

To access tubes, click on the "Picture Tube" icon.  It looks like an old fashioned pen and ink.
If you hover your mouse over any icon, some text should pop up saying what it is.
 
So after you click on the picture tube icon, now click on the "Toggle Tool Options Window".
Click on the picture in there and more pictures should appear.
Click on the one you want and now you can use it.

If you are wanting to know how to make a tube, make sure the graphic is a jpg. 
If it's not, click on "Colors / Increase color depth / 16 million colors (24 bit)". 
Then you have to promote the image to a layer.  You do that by clicking on "Layers / Promote to Layer".
Then just make sure your magic wand is set to an appropriate tolerance, and feather is set to 1 or 2, and click in the background of the graphic and press DELETE on the keyboard.  This will give you a transparent background. 
Now click on "File / Export / Picture Tube". 
Give the tube a name and okay the box. 
However, there are some more settings there to play with if need be.

To change a tubes size, click on the picture tube icon and then the toggle tool options window.
The "Scale" is where you change the size".

~Summer °Ü°