Your question appears to have two parts, given you refer to him both in the midst of Prohibition when he wasn't President as well as after taking office.

Prior to Prohibition, FDR was a moderate Dry and had actually been a favorite of the Anti Saloon League - he even sponsored a liquor control bill in 1913 as a member of the State Senate which got precisely nowhere. The bill crashed and burned partially because once Prohibition began New York would be an inveterate Wet state, but also because given FDR had gone to war with Tammany he stood a snowball's chance in hell of getting any legislation with his name on it passed. (While it never made it into a bill, he also opposed Sunday baseball.)

Interestingly, some of FDR's position may very well have been due to an attempt to make Eleanor happy - Lucy Mercer was a couple years off so their marriage was still traditional and functional at that point - as she was a vehement dry given both an alcoholic father and siblings as well as her interest in social reform. She consistently refused to serve wine at dinners, strongly disapproved of FDR's cocktails, and in 1927 actually tried to get the state police out to raid an uncle who was serving what she felt was too much liquor.

During Prohibition, FDR mostly played the public role of a practical Dry - writing the strong Dry William Jennings Bryan about 'hopeful idiots' trying to get a repeal plank on the Democratic platform in 1924, and supporting it largely because it was still politically costly to oppose the ASL and other supporters even if he didn't believe in it personally. He was correct; the Wet/Dry conflict played a significant role in the Democrats imploding in 1924 and 1928, and Al Smith lost in the latter year not just because of his Catholicism but because that was inseparably intertwined with his vocal Wet views.

But that was FDR's public stance. In private? He started off Prohibition drinking champagne with Harvard friends at the Met Club, continued his cocktail hours throughout it, and like almost all the rich basically ignored it - because it was still legal for him to do so. Prohibition was vastly biased towards the rich, and one of the biggest ways was the tremendous loophole that almost all took advantage of: it was not illegal to consume alcohol that had been purchased prior to Prohibition. This meant the wealthy and their private clubs stockpiled warehouses full of their favorite drinks (FDR wrote a friend he'd bought 4 crates of Old Reserve to remain on the wet list) and essentially spent most of Prohibition sneering at the lesser saps who would never be members - and who didn't have a basement full of legal booze. The wealthy could also travel to foreign shores to satiate their needs, and keep in mind for FDR in particular Campobello is located in...New Brunswick.

But as a candidate in 1932, FDR openly advocated reform for a very simple reason: the government desperately needed the money from excise taxes, and as I wrote in my previous answer on Prohibition's fall, the draconian penalties of the Jones Act had in any case galvanized public support towards repeal.

I'm not aware of any personal attacks on FDR for his personal use of alcohol during the campaign or his first months in office, but in any case he was a vigorous Wet at that point and it took less than 9 months after his inauguration (amusingly, FDR had already eliminated the Prohibition Bureau a month earlier!) to have Utah become the 39th state to ratify the 21st amendment on December 5, 1933 and formally repeal Prohibition.