You have to tape them up as shown in link that Poochieheaven has posted...and leave them up for 3 days so make sure you tape them good so he can't get it off....than take the tape off for 1 day, if after that one day they are not stand retape for another 3 days, if they are standing leave them alone until they fall. I had to tape Harley's ears up and it took almost a month for them to stay up and he has kinda big ears for a yorkie
hope he grows into them LOL...you just have to be consistent with the taping and shave the hair off the whole ear weekly to keep the weight off, the hair grows back quickly so don't worry
Harley is 5 months now and its been atleast 6 weeks since I last taped them.
Here is a link to help you
Jon-An's Yorkshire Terriers (How to train Yorkies ears to stand)