quick topping question

so ive just been letting this plant i started from seed just grow havent used anyting but tap water and miracle grow just want to get an idea of the nature of these plants before i get more invested. any way i was going to attempt my first top and wanted soe advice as to how and where should i just pinch it off or cut it with scissors ive heard of both being done any where here are pics of the top 2 branches thanks fellow growers
 
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