To teleport an armorstand to an item, as you say in your title:
/tp @e[type=ArmorStand,name=Red] @e[type=Item,...]
Where ... is whatever you're using to identify the item (name? scoreboard value? location?).
To spawn an armorstand at an item, as you say in your question:
/execute @e[type=Item,...] ~ ~ ~ /summon ArmorStand ~ ~ ~ {CustomName:"Red"}
Again, where ... is however you're identifying the item. I'd recommend using a scoreboard value based on their item ID, like this:
/scoreboard players set @e[type=Item] isRedWool 1 {Item:{id:"minecraft:wool",Damage:14s}}
Where isRedWool is a dummy objective.
The easiest way to move one entity to another is this syntax of /tp:
/tp <Target Selector> <Destination Selector>
This teleports the target entity/entities to the destination entity/entities.
For example, for your situation, to teleport the ArmorStand within 1 block of you to an ArmorStand at least 1 block away from you:
/tp @e[type=ArmorStand,r=1] @e[type=ArmorStand,rm=1]
You can also use /tp with either absolute or relative coordinates, like this:
/tp <Target Selector> <x> <y> <z>
For example, to teleport the nearest ArmorStand to x=0, y=64, z=10 you could do:
/tp @e[type=ArmorStand,c=1] 0 64 10
Or to teleport an ArmorStand called "Decoration" up 2 blocks and to the north one block, you could do:
/tp @e[type=ArmorStand,name=Decoration] ~ ~2 ~-1
Note that a ~ before a number means the coordinate is relative to the entity's current position. e.i. moving 2 blocks upwards rather than to the absolute value of y=2.
Selecting and moving entities around is fairly easy, but requires some basic knowledge of different command parts. You could use these wiki links to learn more about:
Best Answer
You edited your original comment so now I understand that you meant that you should make it a marker. This got fixed now in 1.15.2 pre1 like you said it would in the comments. Now I also realize that you thought I wanted the armorstand to be visible which I don't.
So answer is summon the armorstand as a marker with glowing and only the item on its head will glow.