I have a new pen for my iPad mini and need to charge it. How do I start?

First, ensure that the Apple Pencil (?) is compatible with your iPad mini. You should note that only the iPad mini5 supports Apple Pencil - and for this model of iPad you will require a first generation Apple Pencil (that features a removable cap - beneath which is a Lightning connector). Earlier models of iPad mini do not support Apple Pencil.

NB: The first and second generation Apple Pencils are not interchangeable. The second generation Pencil is not compatible:

Apple Pencil compatibility - Apple Support

As for charging the Pencil, see >>> Charge your Apple Pencil and check the battery - Apple Support

See instructions in Charge your Apple Pencil and check the battery - Apple Support

What year and model iPad Mini with which version Pencil?

FYI, No Pencils works with any iPad Mini models made before 2019.