I don't think You went to the right link for setting up a static ip. The link from step 2 that give a guide for setting up a static ip is for windows. But The link I gave you in step 1 is from the Linksys support site. The instructions look fairly clear. Click on the link from Step 1 above. Without a Static IP, port forwarding will not be successful.

In fact I'll copy it here:

In order to configure the router with a static IP address, you will need the following information from your ISP:

IP address
Subnet Mask
Default Gateway
Domain Name Server (DNS) addresses

Access the Router's web based utility by typing http://192.168.1.1/into your web browser.

A password window will appear.

Leave username blank and enter the password as admin (all lowercase).

Click OK.

Once on the Setup page, go directly to the WAN IP Address or WAN Connection Type, and change the option from Obtain an IP address Automatically to Specify an IP Address.

Enter the IP Address, Subnet Mask, Default Gateway, and DNS you retrieved from your ISP.

Scroll down and click Apply.

If settings are successful, click Continue.

The Router is now set up for use with your provider and a static IP address.

(By the way ... Some of this information needed you will find in your control panel. I can't remember which one it is, either Configuration Manager or TCP/IP or Internet.)