In the most simple terms, they didn't really do much. There was an insistence from the PG that people were going to have to wait for changes like constituent assemblies or land redistribution until after the war had ended. The original leader of the PG, Milyukov was also forced to resign after he promised the allies that he would continue fighting in the war, so the leadership of the PG was weak.

Further revolutionary actions such as an attempted revolt during the 'July Days' and also an attempt to seize power by general Kornilov led to the provisional government looking weak. What made this worse is that the Bolsheviks helped to defend Petrograd from Kornilov and his troops, the Bolsheviks were beginning to gain favour over a 'weak' provisional government.

Along with these weaknesses of the PG there were also the strengths of the other groups. The Petrograd Soviet had strong members (Trotsky and Dzerzhinsky) who set up the Military Revolutionary Committee which led to them supposedly being in control of the defence of Petrograd. This committee then gained control of the Bolshevik red guard and by the time the new PG leader, Kerensky, could do anything about it the city had already been seized.

Sources: Sally Waller 'Tsarist Russia 1855-1917' and Martin Sixsmith 'Russia: a 1,000 year chronicle of the wild east'.