This is the 14078th most frequent Russian word.
ознакомившись
"Having familiarized oneself."
The usage of "ознакомившись" here shows an action completed prior to the main action in the sentence — familiarizing oneself.
Ознакомившись с правилами, он начал игру.
Having familiarized himself with the rules, he started the game.
This demonstrates "ознакомившись" as a participle indicating a preliminary action leading to a subsequent feeling or state.
Ознакомившись с материалами экзамена, она почувствовала уверенность.
After familiarizing herself with the exam materials, she felt confident.
Here, "ознакомившись" indicates an antecedent action that provides the context for the decision-making process.