Hire an electrician to install a dedicated sub-panel in the garage. With that installed, you can isolate the power and install 240 volt and 120 volt outlets by yourself. If you’re unsure, you can pay the electrician to inspect and do final hookup after you’ve installed boxes and wiring. Invest in a diy book on house wiring available from Lowes / Home Depot, (thumb through it to make sure it’s something you’ll be comfortable learning and doing.