Re-root a tree?

Hello, I have one question about ‘re-root’.

After using the command ‘tree.shared’, I want re-root the tree where I want. Using the program FigTree, I can re-root the tree, but the length between root and each tip are not identical. I want to make a tree with same branch length such as the default tree from the command ‘tree.shared’.
How can I make this kind of tree?