|You probably don't have a wireless high speed modem, unless it's a less common one that connects to cellphone towers rather than a telephone line or coax cable connection..|
In most cases it's either a combo router / high speed modem, or a standalone wireless router connected to a standalone high speed modem.
"Do you have a wireless network card installed and properly running on your computer?"
You must have drivers for the wireless adapter that work in Win 98 installed, Device Manager must recognize it, and you must install and use a wireless configuration program provided for the wireless adapter that works in Win 98 to set up the wireless connection to the combo router / high speed modem, or a standalone wireless router.
The wireless broadcast must be enabled in the combo router / high speed modem's , or standalone wireless router's configuration settings - if you haven't used the wireless feature previously that's often disabled by default.
If you use wireless security settings, the settings on both ends of the connection must be compatible with each other - in the wireless adapter's and the combo router / high speed modem's or wireless router's settings.
If you can't connect to the combo router / high speed modem or wireless router wirelessly, you must connect to it by means of a network cable connection from the same computer, or by means of a network cable connection or a wireless network connection that is already working on another computer in a local network connected to the same combo router / high speed modem or wireless router.
The default URL - 192.168.xxx.xxx - you use in an internet browser program to access the combo router / high speed modem's or wireless router's logon screen, and the default user name and password you need to use to access and change it's configuration settings, are in the full manual for the combo router / high speed modem or wireless router.
If the combo router / high speed modem or wireless router is already using wireless security settings, copy down the type of encryption, the channel, the SSID, and the encryption key or password and use that info to set up the wireless adapter's configuration settings on your computer.