As far as I know, the rebellion was a planned affair, and as with many failed rebellions. No one was really prepared for a civil war, it was supposed to be relatively bloodless and a quick coup, but I do not know almost anything about the offical plan of action so to speak. What was supposed to happen according to their plan when the red lantern was raised in Helsinki, 28th of January?
No revolutionary plan to take whole of Finland has been identified. When the revolution was started in the end of January the Finnish Red Guards had two plans going on simultaneously, one for taking control in Helsinki and other major cities in the south. The other plan was the mobilization of local guards across the Southern Finland to protect the Great Weapon Train coming from Petrograd.
The first plan was pretty much a run of the mill coup plan. It included the arrest of political opponents like the senate and taking control of means of communication like telephone centers and railroads. Outside the capital the targets for the coup were left to local Red Guards to decide.
The plan to Protect the arms delivery from Petrograd called for mobilization of Red Guards for three days. The rail lines the train would use were to be guarded from White Guards. Russians were hardly involved in these plans, which is shown by their orders during the first few days of the civil war to only fight if attacked.
The Reds had noticed that their precense in the Northern Finland was weak and that they could not take control of those areas with the coup. They had no concrete plan for taking those areas with an offensive and their military moves once the war started concentrated on protecting their own positions, not exploiting the initiative their greater weapon stocks gave them to crush the Whites early.
The Red vision for victory rested on ideological belief in the spreading of the revolution once started and in Russian support. They wanted Whites to attack Russians first to make sure that Russian bolsheviks would be involved. However they miscalculated the amount the Russians were willing to get involved. The Soviets in Petrograd had bigger problems like German invasion at the time while the numerous Russian troops in Finland mostly just wanted to go home, tired of the war.
One should remember that the Red plans were made mostly by civilians, in a committee under enormous pressure. The situation was escalating fast with fighting between Reds and Whites having already started a week earlier in Karelia in and around Viipuri.
Main sources: Punakaartin Sota, osa 1, (Red Guard's War, part 1) by Jussi Lappalainen.
Tie Tampereelle, (Road to Tampere) by Ylikangas