ok.
How large is it? you need it to be on a surface where the entire quilt can lie flat. A table is generally better than the floor where possible.
Lie the backing fabric down, then the filling then the quilt top.
you want to baste it together in both directions. I think how close together the basting stitches are depends on the size of the quilt but not sure. I did a double bed size, and basted at 10cm intervals.

When you have basted the whole thing you can quilt it.
Depending on what you have inside the quilt, is how close togther the quilting will need to be - some requires 2.5cm as the maximum 'gap' between quilting, others can be more or less. If you quilt it too far apart the inner can tear when you wash the quilt.

You can also pay someone to quilt it for you, but thats less personal, or you can buy a quilting loop and hand quilt it.