18 month old potty training

my son will be 18 months old very soon and he is a very tall solid boy (size of most 2 1/2 year old) he is showing signs of being ready to potty train like tugging at dirty nappies and getting shy when he is doing a poo in his nappy if people are around . Iv put him on his potty a couple of times now and both times he has done a wee 👍 my question is how do they tell you they want to go if they are not yet talking ? he has not long become confident in walking and can say about 12 words and a few short phrases , do I treat it like teaching him any other word ? I'm guessing I just say the choice of word for going to the toilet as I take him to it and sit him on and again after he uses it ? as he isn't at the stage of physically asking me for things I'm wondering how he can let me know ...