Open the inventory/backpack from the hamburger menu in the top-left corner, then tap Inventory or the backpack icon. In Roblox itself, that’s the standard way to open the backpack on mobile, and a Brother’s Vow wiki lists B for inventory on PC, which matches the same system on desktop.

Mobile steps

  1. Tap the three-line menu in the top-left.
  2. Select Inventory or the backpack icon.
  3. Tap the item you want to equip or move.

PC shortcut

  • Press B to open inventory/backpack.

Small note

If the game’s UI feels different, the backpack may be tucked under the same top-left Roblox menu rather than shown on the main screen. TikTok posts about Brother’s Vow on mobile also point to opening the backpack/inventory through the mobile menu flow.

TL;DR: On mobile, use the top-left menu → Inventory/backpack ; on PC, press B.