wifi not working

It´s the first time using the board yun, arduino.org.
i have read that automatically a wifi is created.
there is not this wifi.

i can see the board in /dev/ttyACM0.
I can send sketches to it.

How can i fix it?

I tried a upgrade using the SD CARD but nothing happened.

Is there a way to upgrade using the USB port (not the micro usb)

Is there a sketch to verify if the yun is working?

the led white sometimes blink.

To see if a WiFi connection is made check your routers DHCP list.
If it has made a connection it will be shown in there and you can access it via that IP address.

A better way to ensure access is with the Ethernet port to start with until you are a little more comfortable with the board.

Using the SD card often requires a basic knowledge of LINUX.
There are plenty of useful help on the internet for that aspect.

Not sure what you mean by upgrade the USB port (host port) ?

Upgrading the YUN itself can be a little problematic and there are at least three ways to do it and at least that many variations on the Linux distribution used.

It pays in the forums to be as detailed as you can with every single issue as it is more likely to get you a better answer.

Thanks for your answer.
I am starting using arduino.
I bought UNO Mega 2560 and some shields.
I don´t have problems to use them.

I bought yun and after read a lot of things about it,
I could not see the ssid.

After all, there is a problem at the boot.

If you connect it to your router with an ETHERNET cable and give it a minute or two can your router see and IP in the DHCP list ?