Standing with feet shoulder width apart. Bottom squeezed and stomach engaged. Holding the bar/weight with elbows tucked, arms fully extended. From there, lever the arms up lifting the bar to chest height, always keeping elbows tucked in for support.
Important: If the weight feels a little light, create tension in the arms by squeezing the weight, then keeping that tension, lift the weight. Suddenly it feels a lot heavier. Other alternative is to increase the speed of reps.
If weight is too heavy, then choose a lighter load, or indeed find light dumbbells and do alternate bicep curls.