Бол - to be, болдум - was (past tense). Мен үйдө болдум - I was at home. When you say so, native speakers know that you were at home last time (yesterday, in the morning or before you said it). Эле - past tense of incorrect and insufficient verb of to be. Мен үйдө элем - I was at home. This requires a qualifying word/sentence/condition. Сен чалганда мен үйдө элем - When you called, I was at home. Even though you do not specify native speakers know that it was a fact/conditions that you was at home.

Уйдо болдум- I was at home. Уйдо элем-I am at home.