How to upload songs to iTunes

Luul,

Your question is a bit vague. But if by "upload" you mean you have created original music and wish to make it available for sale in the iTunes Store, see this:

iTunes - Working with iTunes - Sell Your Content - Music Provider: FAQs - Apple (PH)

Hi,

You don’t indicate os or version of music (iTunes) app but See Ways to add music to build your library in Music on Mac – Apple Support (UK)

Jim