To find it out, you have to complete three disguises which remain in the apartment. So first search Holmes' bedroom.
Take boots from under the armchair,
trousers from the other armchair
another boots by the mannequin
a hat left on a table top of dresser,
jacket from a bed,
and hat lying on a cart, nearby door.
Return to living room, from where pick up trousers from a couch.
Take also a jacket from a fallen chair nearby the table.
And don't forget about shoes lying among few pairs nearby a fallen cupboard.
Pick up also trousers from a floor, nearby another cupboard.
And from a hanger standing nearby door to Watson's bedroom, take another jacket and hat.
Now, you should have three pairs of shoes, trousers, three jackets and three hats. With all that stuff go to the wardrobe and open it.
Now you have to group gathered clothing and add a proper envelope to each one. You can look at everything through a magnifying glass, what I recommend.
On wardrobe's door you have a priest's hat for sure, but the jacket isn't his. Look at the one from a middle set: it's stained with stearin, so swap it with the first one.
Trousers on the door aren't priest's but captain's - replace them with trousers from the third set.
Blue hat from the second set fits to captain's set, so switch it with the brown one.
Remaining shoes: dark grey should be in the first set, light grey in second and brown at the third.
Now it's time to assign envelopes. The first set is priest's, so put a proper envelope (with a brown stamp). The last one belongs to captain, so put an envelope with red stamp in front of it.
The second set - is it labourer's or clerk's? Examine trousers with glass to examine them - they're stained with an ink. So put a clerk's envelope next to it. When it's done, Watson will comment it and you can change anything. Above you can see how it should looks like.
(A success gives you next achievement: "Desperately Seeking Sherlock").
So, you know that Sherlock has a labourer's disguise and is in Whitechapel. According to Watson's suggestion, choose this quarter on a map, and then click on a main street.
Watson deduces that he needs money. So go to his bedroom, open a desk and notice that someone searched his wallet.
Choose again Whitechapel on the map.