A newbie attempting to merge video & audio files

[gillsimo]

Hi...more an imposter than a newbie as I've never been into video & probably won't be in the future.
I was charged with recording a three hour seminar which predictably proved a mistake because I captured the entire video but managed to do so without sound.
I've since aquired the audio file of the event & would simply like to add this to my silent video.
I've attempted this with several free tools but all have a size limit way below my 3.2GB video file & I'm already pushing my abilities so splitting/joining several parts is, I imagine, a nightmare that I'll never achieve successfully.
So please...might someone be able to suggest a free, or as cheap as possible, means of achieving my aim....because I'm very unlikely to ever need to do this beyond this one-off instance.
Thank you/Gill

[manono]

You should provide the current formats (codecs) used for the audio and video and your intended output format (container). If you don't know, provide the text file MediaInfo shows for the audio and video.

[ProWo]

You can mux them with MkvToolNix

[butterw]

It's a good idea to post the mediaInfo output for the audio and video files.

Muxing video and audio is not actually difficult.

Synchronizing could be more troublesome: hopefully you have video and audio that starts at around the same time and with the same length (no cuts in recording).

[gillsimo]

Thank you for your replies...'tis very nice of you's to take the time.
With respect, I'm thinking that I'm perhaps asking too simple a question to folk who delve too into video than said question warrants.
I have a single mp4 video file & an mp3 audio....I've tried several free/trial software, all are perfectly adequate for my needs, all offer a timeline on which to place video/audio tracks & those tracks can be moved on that timeline.
So...no editing to be done to either, I simply nudge the audio into sync (my idea of sync perhaps) with the first person speaking to camera & three plus hours later that sync remains.
My problem is that I can't find a free/trial or cheap enough program, no more complicated than those already used with ease, that will allow the finished product to be rendered & saved....there is always a 1, sometimes 2GB max limit.
I was therefore asking if there was a simple, basic, software that a fool such as I can get along with, as I have the others...but which allows for a 3GB + file to be rendered & saved.
Apologies if I'm somehow mistaken but I can't imagine that I need to venture into the links kindly provided in order to find my answer?

[ProWo]

The simple way. Download MkvToolNix and unpack it to a folder somewhere on your computer.
Doubleclick mkvtoolnix-gui.exe into this folder. In the new window that opens, drag and drop your video file into the upper section. Do the same with your audiofile.
Click on Start multiplexing (at the bottom, in the middle). Done.