interactive brokers moc order in which one asset sell than other buy

[bharteshjain]

hello everybody

I am new to this forum so if posted in wrong section than please point to the right direction

I am beginner trader and have just opened account in interactive broker.I want to implement relative momentum strategy in my account.For example on monthly close price if i want to sell spy and buy tlt on closing price or as close to it . I understand i need to make basket orders but How to add this order i am not understanding.
please help me
thank in advance