Glow ink sacs are the most important resource in the production of both glow item frames and glow signs. That said, you can get these glow ink sacs from glow squids in the game that you can find in the deepest parts of the ocean.
However, we recommend making potions of water breathing or an enchanted helmet with a respiration enchantment of two or one. You can make the potion of water breathing with one nether wart, one pufferfish, and one water bottle inside a brewing stand.
But to get the enchantment, you will first need to find the book and then use it in either an anvil or enchantment table. We also recommend getting a sword with the loot three enchantment along with water breathing potions or an enchantment helmet.
This is because, without the loot III enchantment, you will be missing out on an increased loot drop rate for the ink sac of 6 instead of a max of three.
Related: How to Make a Glow Item Frame in Minecraft
After this last part, you will be set to go glow squid hunting, and we recommend building a boat and finding a nice space of open water to search. Once you find a squid and get the scac from them, you can then use it to make either a glowing item frame or sign.
How to make a glowing item frame in Minecraft
To make a glowing item stand, simply make a item frame and then place both the glowing ink sac and the frame next to each other in a crafting table. When you have the glowing item frame built, you can then use it just like a regular item frame, but this will glow in the dark.
How to make a glowing sign in Minecraft
To make a glowing sign, simply place a regular sign down and then put some text into it. After this, place your glowing ink sac in your hot bar and then right-click the sign, this will then illuminate the text. If you want to change the color of the text, grab some, dye, and right-click the text, this will in turn make the text on the sign glow that color.
For more on Minecraft, check out How to Make a Glow Sign in Minecraft and Where to find Glow Squids in Minecraft