Backup your dlc3_vox.csv and then start changing the sounds in it to the ones you want and convert the sounds.

any specific place on putting the new sounds?

plr_0_vox_crappy_0,voiceovers\zombie\new\Player0\weappick_crappy_00.wav,,,,1,1,75,1700,2,reject,1,reject,voice,,curve2,0.8,2100,,curve2,1,1,,3d,streamed,,,master,,,,,,0,,,,50,500,0.9,0.5,,,,,,10,25,0.25,1,,

Well, this isn't really a big issue but first I'll let you know I've found out a while ago that it isn't required to use unsigned 8-bit PCM as your format and actually just degrades the quality of the sound. I set my sounds to signed 16-bit PCM which gives them better quality while still having compatibility with COD5.

Here's a list of things to check:

1. Did you set the project rate to 44100hz?
2. Did you set the track rate to 44100hz?
3. Did you set the sample format to 32bit float?
4. Did you clear tags?

Here's an image of my export settings if needed:

Spoiler: click to open...

[close]

If you're talking about what is in the csv you will want to replace what is already in there otherwise you won't ever hear them since the scripts won't ever tell the game to play them. Don't change the first part of the alias line, only the file path to correspond with your sound.
For instance this

plr_0_vox_crappy_0,voiceovers\zombie\new\Player0\weappick_crappy_00.wav,,,,1,1,75,1700,2,reject,1,reject,voice,,curve2,0.8,2100,,curve2,1,1,,3d,streamed,,,master,,,,,,0,,,,50,500,0.9,0.5,,,,,,10,25,0.25,1,,

leave plr_0_vox_crappy_0 alone and only change this part voiceovers\zombie\new\Player0\weappick_crappy_00.wav

If you're talking about the custom sounds that you have obtained and want to use as the voiceover then you will need to convert the sounds. Look up a tutorial for converting sounds for waw (ex: custom music box songs/main menu music). Just instead of making your own soundalias and including it you won't have to do since dlc3_vox is already included in all DR style maps.
Also keep this in mind