You really should obtain an owner's handbook - and read it.
Some 2-stroke engines used an oil injection system which is or was considered superior to mixing oil and petrol which is fine and dandy if it works ok and if the rider can remember to top up the oil container - if it works and is topped up there is no need to mix oil with the fuel.
Some oil injection systems proved unreliable and some riders proved unreliable and both scenarios result in expensive engine damage.
Many more experienced riders opt to forget the oil container and play safe by mixing oil with the fuel while others continue to use the oil injection system, insisting it is adjusted so there is a hint of blue smoke from the exhaust proving it is working.
There should be a mechanical release fitted. Insert your ignition key. Push the key away from you, further into the key hole. While pushing the key turn it counter clockwise, the wrong way. The seat should 'pop' open.