You can upload videos to YouTube in a few easy steps. Below you can find the necessary instructions to upload your videos from a computer or from a mobile device.

Computer


To get started uploading videos on YouTube from your desktop, follow the steps below:
Sign into YouTube.
Click the Upload button at the top of the page.
Before you start uploading the video you can chose the video privacy settings.
Select the video you'd like to upload from your computer. You can also record a video from your webcam, create a video slideshow or import a video from Google+.
As the video is uploading you can edit both the basic information and the advanced settings of the video, and decide if you want to notify subscribers (if you untick this option no communication will be shared with your subscribers). Partners will also be able to adjust their Monetization settings.
Click Publish to finish uploading a public video to YouTube. If you set the video privacy setting to Private or Unlisted, just click Done to finish the upload or click Share to privately share your video.
If you haven’t clicked Publish, your video won’t be viewable by other people. You can always publish your video at a later time in your Video Manager.


Android

The easiest way to upload videos from an Android device is to use the YouTube app.
Sign in to YouTube.
Open the Guide in the upper left corner of the screen and navigate to Uploads.
Touch the Upload icon at the top of the screen.
Select the video you want to upload.
Adjust the title, description, tags and privacy settings of your video.
On supported devices, you'll also see a video preview with trim handles below it. Drag the trim handles to edit your video's length. A long press on the trim handle will allow you to zoom into a frame by frame view for exact trimming.
Touch the Upload icon.
Tip: Go to Settings > Uploads to modify the type of connection used to upload videos. Use this setting to restrict uploads to Wi-Fi only.

IOS

You can upload videos from your iOS device directly from the YouTube app. Make sure you have the latest version of the YouTube iOS app installed. Follow the steps below:
Sign in to YouTube.
Open the Guide in the upper left corner of the screen and navigate to My Channel (or directly touch theUpload icon on the guide.)
Touch the Upload icon at the top of the screen
Select the video you want to upload from your Camera roll and touch the confirmation button.
Adjust the title, description, tags and privacy settings of your video.
Touch the Upload icon .
Tip: Go to Settings > Uploads to modify the type of connection used to upload videos. Use this setting to restrict uploads to Wi-Fi only.

Source:http://www.asifawalesblog.com/2016/09/how-to-properly-upload-videos-to-youtube.html?m=1