My avatar always has this white shirt and shorts on???

[Vogue14x]

I click for my avatar to take everything off so I can put on other outfits, but this white shorts and top wont go away!! When I put something else on her, it just goes over it and it looks hideous ! Why am I not able to take it off??

[Syo Emerald]

Its part of your skin. You have to change your skin to get the shirt and the shorts off.

[Knowl Paine]

You are wearing a Vanity Skin.

You can get a different Skin and Shape by visiting Market Place (linked above in Shopping), or an Inworld Store.

 

 

[Irene Muni]

You are wearing what is referred to as a modesty skin. You can get a new skin that does not have that underwear layer. In your default outfits (Inventory > Library) you can find some skins for nudity. Of course you can buy a new skin Try Demos) or you can find free ones in world or at Marketplace.

[Nalates Urriah]

The others are right. The shirt and pants are built into the skin.

However, there is a free anatomically complete skin in the Library in your inventory. I think it is the Clubbing Outfit. The male skin is somewhat incomplete. There is no exterior male plumbing in the Library, AFAIK.

So, if you are male, you have a quest before you...

Zindra is the adult continent. Use the world map to find Adult Hub. Fishergate is a region in the adult continent. There will be a load of places that provide the missing genital details and parts for both genders. At the help center you can talk to people and ask whatever questions you have.

Depending how complete you want your avatar, there are numerous options. There are many free genitals. Some are ...functioning... parts. Some aren't. The cost ranges from free to several hundred L$. The scope of operation extends from appearance only to the complete female cycle that goes all the way through pregnancy. It's all about imagination. 

Since you appear really new to SL, I suggest you NOT spend big bucks on completing your avatar. There are brands of genitals. They ...work... best when the brands match. So, you may want to build a circle of friends and find what they use.