WHOAAAAA STOP RIGHT THERE.
First thing first, unless they are done for a season and it is a ONE year league... never EVER drop Malkin, Crosby, Stamkos, or Ovechkin.
Just don't be the newbie who makes that mistake, don't.
As for IR:
If you are on Yahoo, then they will get IR eligibility the day after they are officially placed on IR by their real life NHL team. If you are on another more robust system, there may be fantasy league methods to place a player on IR manually.
Most commonly, teams will not place a player on IR if they think that a player has a chance to play. If a player is placed on IR he has to stay on IR for a minimum of 7 days from the day he was injured. There may be other factors that have to do with cap management/player contracts that I'm not too familiar with but have seen mentioned.
10 Team Yahoo Roto
Keep 3F, 1D, 1G (to max 2 years unless franchise keeper)
3C,3LW,3RW,4D,2G,2BN,2IR Roto-play 85games/position
Player: G, A, +/-, PIM, PPA, PPG, HIT, BS SOG, FW
Goalie: W, GAA, SV, SV%, SHO
C: (F1) Tavares, Stastny, Carter
LW: 1-Hall, Pacioretty, B.Schenn
RW: Mackinnon, Nyquist, Hornqvist
D: 1-Carlson, Josi, Faulk, Franson
G: Andersen, Mason
BN: Jones, Niemi
#- denotes number of years I have kept a player. 2 = I need to trade him this year, (F1) = Franchise Keeper, up to 4 years.