This speaks of Yahweh telling Isaiah what to say as if his words were a physical object Yahweh had placed in Isaiah's mouth. Alternate translation: "I have told you what to say" (See: [[rc://en/ta/man/jit/figs-metaphor]])
Yahweh's "hand" refers to his power. This speaks of Yahweh protecting Isaiah as if his hand were covering him to protect him. Alternate translation: "my power has kept you safe" or "I have protected you and kept you safe" (See: [[rc://en/ta/man/jit/figs-metonymy]] and [[rc://en/ta/man/jit/figs-metaphor]])
The word "plant" means to establish something in the ground. Here Yahweh firmly establishing the heavens is spoken of as if the heavens were a tent that he would spread out and firmly set it in place with tent pegs. Alternate translation: "that I may establish the heavens" (See: [[rc://en/ta/man/jit/figs-metaphor]])
The word "foundation" normally refers to a stone structure that gives support to a building from underneath. Here it describes a similar structure that was thought to support and hold the earth in place. See how you translated a similar phrase in [Isaiah 24:18](../24/18.md).