It's been a while but I think you put the radio in manual mode (man button) then hit the split button. You should see a +/- indicating the direction of the split. You have to program the radio for the amount of split you want. The following is directly from a 29xx dx manual.How does one work split on a 2950? I must have missed that button.
Chapter 7 Offset Frequency Operation
The split frequency function offsets the transmitter frequency either above or below the receiver frequency by a user-programmable amount. This is necessary for operating on FM repeaters. In the following example, the programming of a 1 MHz offset will be described. Before attempting to program the offset frequency, ensure that the radio is operating in the manual mode by pressing the MAN key. NOTE: FM repeaters may require that a sub-audible CTCSS tone be transmitted to gain access to the repeater. The RCI-2950DX/2970DX-150 can be equipped with an optional CTCSS encoder. TO PROGRAM TX OFFSET: 1. Press the PRG (Program) key. 2. Press the SPLIT key. The LCD display will indicate 00000 with PRG and SPLIT showing in the lower left-hand corner of the display. 3. Using the SHF key and the UP and DOWN arrows as described earlier, program the display to read 10000. 4. Press ENT. A 1 MHz offset has now been programmed into the radio. 5. Return the radio to manual operation by pressing the MAN key. 6. Using the SHF key and the UP and DOWN arrows as described previously, set the radio to the desired receive frequency. 7. Press SPLIT. Either "SPLIT+" or "SPLIT-" will be displayed in the lower right corner of the display. If "SPLIT+" is displayed, the transmitter will be offset 1 MHz above the receive frequency when keyed. If "SPLIT-" is displayed, the transmitter will be offset 1 MHz below the receive frequency. When the transmitter is keyed, the frequency display will change to show the frequency being transmitted