"把搁在支架上" can be translated into English as "place it on the stand" or "put it on the support", depending on the specific context and the object being referred to.
If you're referring to a general object being placed on a stand or support, "place it on the stand" is a suitable and common expression.
"Put it on the support" is also a valid translation, especially when the context emphasizes the act of supporting or holding the object.
Both translations convey the idea of placing an object onto a supportive structure.