I know that for "Decir" we use di to command someone, for example: Díme (Tell me).
But how come in this sentence "Dígasela. (Tell it to her.)," we include the g and a ?
I know that "se" is the Indirect Object and "la" is the Direct object, but I don't understand why we included the "ga" in "Dígasela."
In the sentence " Ponte los zapatos. (Put on your shoes.)," we don't use the subjunctive form of Poner like we did for Decir.