How Do I Unlock Mod Slots in Warframe?

In order to unlock mod slots in Warframe, players must first reach the rank of Master with their chosen clan. Once they have done so, they will need to purchase a blueprint for the desired frame from the clan vendor. With this blueprint, players can then take it to the foundry and craft the frame. The number of mod slots available on a frame is determined by its rarity; common frames have two mod slots, while rare frames have three.

To add mods to a frame, players must first select the frame they wish to modify from their Arsenal. From here, they can choose which mods to install from their Mod Collection.