The 2950 switch is layer 2 only. The VLAN interfaces are for assigning a management IP address to the switch but it allows you to put that IP address on whichever VLAN you desire. Based on its design, just assign one IP to one VLAN interface such as "interface VLAN 10".
When a VLAN does not have any ports assigned to it, the "interface VLAN" is in a down state because there are no ports assigned to it.
1 - Create each VLAN with the "vlan 10" and "vlan 100" commands.
2 - Assign every port to one or the other with commands like "interface FastEthernet0/1" and then "switchport access vlan 10". (repeat step 2 for all ethernet interfaces on the switch)
3 - Assign the management IP address for the switch to the "interface VLAN ??" depending on which VLAN that IP address goes to.
4 - Check your work with a "show vlan" and "show ip interface" command. The VLANS will show ports associated with them. The VLAN interfaces will be up.
Remember that on a switch like this, the "interface VLAN ??" is a virtual interface with a presence in a VLAN. Its only purpose is to put the assigned management IP address for the whole switch into one VLAN or another. The VLANs themselves are not represented by the VLAN interfaces, they are represented by a "show vlan" command. If you want to have multiple management IP addresses assigned, that is your choice. It is not a router so one IP address is all you need.