you need to setup the wifi connection and you don't have a display to do it trough graphic interface.
Solution:
You can plug the microSD card into a computer,a new Disk Unit will be available, there you can create a new file (wpa_supplicant.conf) for the wifi configuration file with the details example as you can see later in this same post.
If you have access to the command line ( you have a display ), you can do it using the command line tool once you are connected using ssh, just open the file wpa_supplicant.conf using the following commands:
Just edit the file with the correct SSID and password in the file that have to lloks like:
Source:
https://www.raspberrypi.org/documentation/configuration/wireless/headless.md
# manual edition of the filesudo nanosudo nano /etc/wpa_supplicant/wpa_supplicant.conf
# launch the config setup toolsudo raspi-config
Just edit the file with the correct SSID and password in the file that have to lloks like:
ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdevupdate_config=1country=<Insert 2 letter ISO 3166-1 country code here>network={ssid="<Name of your wireless LAN>"psk="<Password for your wireless LAN>"}
Source:
https://www.raspberrypi.org/documentation/configuration/wireless/headless.md
Hardware:
For old raspberry PI, you will need an wifi USB key like this:
TP-Link TL-WN725N Adaptador WiFi USB inalámbrico Nano, Compatible con Raspberry Pi, N 150 Mbps, Botón WPS, AP soft Windows10/8.1/8/7/XP, Mac OS X 10.7-10.11, Linux, negro