For each system you want to log in to, you need to enter at minimum a Description, application server, System ID or System Number, and SAP System type.

Right click the description and then select Properties.

You can now enter the description.

Enter the application server you want to connect to. This would be either the computer's hostname or its IP address.

Also enter its System ID or SID—a three-character identifier assigned by the System Administrator. Or enter the system number which is a two-digit number.

Choose the R/3 button.  R/3 system comprises all systems except SAP's old mainframe-based R/2 system. 

Now you can click the Save button.