How can I convert 2-methylhexane #C2-C3# bond from bond line notation to Newman projection?

Step 1. Draw the structure of 2-methylhexane.

Step 2. Convert to a wedge-dash structure at #"C-2"# and #"C-3"#.

Step 3. Identify the groups on #"C-2"# and #"C-3"#.

The main chain of hexane is the horizontal zig-zag line of carbon atoms.

#"C-1"# is on the right.

The groups on #"C-2"# are #"H"#, #"CH"_3#, and #"CH"_3#. Those on #"C-3"# are #"H"#, #"H"#, and #"CH"_3"CH"_2"CH"_2#.

Step 4. Draw a template for a Newman projection.

Step 5. Attach the groups to the carbons of your template.

View the molecule from the lower right.

The groups on #"C-2"# go on the front carbon atom. Put a #"CH"_3# group on the top. The other #"CH"_3# group goes on the left, and the #"H"# goes on the right.

The groups on #"C-3"# go on the back carbon. The bulky #"CH"_3"CH"_2"CH"_2# group goes on the bottom, and the #"H"# atoms go on the other bonds.

This is the most stable conformer. It has the bulky propyl group anti to a methyl group.