I got my programmes and the libraries running by creating new projects for the main program and each library. Then adding dependencies as you said.

Solution explorer > dependencies > add project reference > browse
C:\Users\MyName\Documents\VB2\MyLibrary1\bin\Debug\net6.0\MyLib.dll

i included the imports statements

It worked & I thought I was in the clear but when I added another library and I got more errors.

In my main program I went:
VS > build > clean solution
VS > build > rebuild solution
It worked again.

Thanks for your help