64 bit in 1.3.1

[Katieop3]

I have a heavily modded ksp 1.3.1 and I want to go back to play it again after 1.4.1, I need 64 bit to run my mods and it only says "Play ksp, Launch ksp (32 bit)" when I press play, how do I play 64 bit?

[Snark]

Moving to Technical Support.

16 minutes ago, Katieop3 said:

I have a heavily modded ksp 1.3.1 and I want to go back to play it again after 1.4.1, I need 64 bit to run my mods and it only says "Play ksp, Launch ksp (32 bit)" when I press play, how do I play 64 bit?

Just go find the folder where KSP is installed.  It has two .exe files there (one for 32-bit, one for 64-bit)-- if you look at the file names, it's clear which is which.  Just double-click on the 64-bit one to launch it directly.  You don't need to do it via Steam.