The past tense consists of two parts: 1) the present tense of verb to be, 2) and the participle.
The order in which these two parts appear is irrelevant, ’su bili’ is the same as ’bili su’. Sometimes there are even some words between them.
The participle agrees in gender and number with the subject. That means, it has different endings for masculine, feminine and neuter gender in singular and plural:
When we say that someone was at a place, we use the locative case, because we’re telling what their location was in the past.