If you don't know the symbol, you can always use the Symbol Search tool.
Position your cursor in the Symbol cell. To replace
a symbol currently on the quote, click on that symbol. To add a new symbol,
position your cursor at the bottom of the table. The selected cell is
highlighted:

Enter the symbol, then press Enter.
Valid symbol formats include:
the full contract or instrument name including the commodity symbol, month, and year (SPM04).
the root symbol (SP,DJ,C,W, etc.) to display the nearby contract (the futures delivery month with the soonest delivery date, or the option delivery month with the soonest expiration date).
the nearby contract (the futures delivery month with the soonest delivery date, or the option delivery month with the soonest expiration date). For the nearby contract, enter the commodity code and the string "1!" (sp1!, c1!, DJ1!, etc.). Likewise, forward designated contracts may be selected using "2!" (2 months forward), "3!" (3 months forward), etc.
a mathematical expression, using one or more contracts, numerical constants, and simple mathematical operators (+ - * /). Examples:
(ng1! + ng2! + ng3!) / 3
w1! - c1!
ES / SPY * 100