Im not sure you are understanding. You can have regular numbers in a confrence call. You also can add them to you contacts. You also dont have to bring them all in at the same time.
First off lets start by showing you how to add regular numbers to your contact list.
1. Click the "add contact" button at the top right of the screen.
2. Now click " add ordinary phone number to skype out contacts"
3. Enter the name of the person you would like to add. ( Any name even if they dont have skype )
4. Now click the little "flag" icon, and make sure the correct country is selected. ( the country in which the person you are calling lives )
5. Now enter the phone number of that person.
There you have it. A regular number saved in contacts. The contact should have a little blue icon with a white phone next to there name.
Now If you want to create a confrence call, but dont want everthing to end up a mess, make sure to bring one person in at a time, and let them know whats going on.
Start by either by calling a landline number IE, click on the "call phone" tab, and calling the phone number of your choice. Or you can call a skype contact. It doesnt matter.
Once they answer let them know whats going on, and that you will be creating conference call. Tell them to hush while you call the next person

1. Now click "add callers".
2. You will have a box that pops up. In that box you can either select a regular contact from your contact list. OR you can type in a phone number. ( skype will will know the diffrence ) Make sure to select the country you are calling.
5. Now click add
6. Then start
You can either add a bunch of phone numbers at once, or repeat the steps that i just showed you. This way you can tell each and every person you are calling, whats going on.
I hope this helps. Like I said you CAN add a person from a regular land line to a confrence call. If you have any more question, please feel free to give me a call, and ill help walk you threw it. This should help.