First, let's setup a Gnosis Safe Multisig with the same access/control structure as your old multisignature wallet.
Step 1: Open wallet.gnosis.pm
Step 2: Select the multisignature you would like to migrate
Step 3: Initiate Safe Creation
A pop-up will open explaining the benefits of the new Gnosis Safe Multsig. By pressing on the "Create new Safe" button, you are taken to the Gnosis Safe Multisig interface.
Step 4