It is a bit confusing for a puppy to learn to use multiple places to pee and poo. So you will have to be a little more patient with him and be understanding that he will take a little longer.
Newspaper training comes in handy in these cases. Next time he pees, put a newspaper on it. Then put the news paper in the toilet. This will "mark" the bathroom and will tell your puppy it is ok to pee in the bathroom.
Next, step is to get him to pee there. You must already be familiar with his toilet schedule. So when it is time for him to pee, just put him on a leash, as if you were taking him out. But instead take him to the bathroom. He might not pee, because he thinks it is not ok. So, the first time you might have to wait a very long time. But have patience and don't give up. Just wait there. He will finally not be able to control himself and will relieve himself.
At this point, explode into a little celebration. Praise him in a very excited voice, run to his treat box and treat him. Pet him copiously. Basically make him so very very happy about this little act of his. You just need to repeat this mini-pee-party 3 times. You will be surprised how quickly he learns to be so happy about peeing in the bathroom. Subsequently, you only need to praise and treat when he gets it right, and ignore when he gets it wrong.
If he has accidents, clean with a 50-50 mixture of vinegar and water and disinfect, so that there are no traces of his pee in the house. This will reduce the risk of him peeing again at the same spot. But be SURE not to yell or scream or punish him for accidents. That is negative attention and he might continue doing the same. Just ignore and clean up. It will definitely work!