How can I go to column B?

I realize that 400 people have already asked this question, but as a newbie I have to learn. SO: HOW DO I STEP IN COLUMN B TO GET USHIWAKAMARU??

I realize that 400 people have already asked this question, but as a newbie I have to learn. SO: HOW DO I STEP IN COLUMN B TO GET USHIWAKAMARU??