1. Mobilize a factory to military use
2. Put the nation-specific units in the Reserve Units section (or increase shipbuilding)
Sort of...Pick the combination you want (see the back of the Battle Manual), shipbuilding is immediate (remember increasing GER/ITA shipbuilding gives GBR/FRA +1 support permanantly). Units go onto the turn track as many spaces ahead as given on Table 14.83 (Rulebook), for example air units are placed 4 turns in the future.
3. That turn or a later turn, spend 2AC + 2 tile points to place a unit on the turn track the appropriate number of turns further on
At the start of a turn when there's units on the turn track, they get moved to the respective Nation's reserves. It can be build for 2AC & 2TP that turn, subject to the restrictions in 18.4.
4. When that turn arrives, place the unit in the Active Units section, and on the Balance of Power chart
Any turn where you build a unit (Economic Segment) it gets moves to Active, and you add the Balance of Power counter. This is done before you start the Diplomatic Phase (in case you change the Balance of Power/Russian Garrison requirements).
For example, I'm playing Russia and mobilise a factory in Spring '37. I place an infantry in the Summer '37 box, an air in Spring '38 and an armour in Summer '38.
At the start of the Summer '37 turn I move that infantry to my reserves, where I can pay to build it in the same turn. At the end of the Economic Segment I declare it and move it to my active units.
Hope this helps.