To add a new symbol, you need to know 4 items – symbol, exchange, tick increment and point value.
First add the symbol first in TWS (example using SI)
1. the Underlying is the symbol – symbol is SI
2. exchange – exchange is NYMEX
3. look at the bid(29.715), ask(29.735) and last(29.660) prices – the best guess is that the price changes 0.005 per movement – tick increment is 0.005
4. right click the symbol in TWS,select Contract Info, then Description – in the pop-up window, look for the Multiplier (this is the value per whole point) – multiplier is the point value – point value is 5000