The 24-year-old joined Becky Langley's side on Friday and could make her United debut in Sunday's FA Women's National League Northern Premier Division clash with Nottingham Forest at Kingston Park (kick-off 2pm GMT).
And forward Lumsden believes the fact the Magpies' aspirations match her own helped pave the way for her move up from the South Coast.
"It's a very long way away from Portsmouth so it was a big decision, moving away from home – I'm actually from London, and it's still a distance from there," she explained.
"But, obviously, the ambition of the football club and my aspirations in football matched what Becky wants to do with the football club.
"It is definitely the perfect fit."
Lumsden and fellow January recruit Lilie Woods linked up with their new teammates ahead of the weekend visit of Forest, with Langley's charges looking to preserve their unbeaten league record on Sunday.
The prolific striker – who bagged 27 goals for Oxford in the 2021/22 season – is keen to help fire her new club towards promotion.
"Goals are what you love doing but anywhere I can help the team would be great," she said.
"I just want to do what I can to help the team get promoted.
"It is an exciting time to be a part of the football club and with the fans behind us, we can go far as a club and as a team."
Lumsden says she has settled in quickly at United, who have enjoyed a sensational start to the 2023/24 campaign and currently sit five points clear of Burnley at the top of the table.
And she admitted that Newcastle's vibrant and committed fanbase is another aspect of the club that helped entice her to the North East.
"It's been really good - everything is new at the moment but I have settled in well," she added. "The girls have been fantastic and welcomed me and training has been good.
"It is a massive statement in women's football, the amount of fans that Newcastle get down at football matches. So many people in Newcastle just love football.
"It's exciting and I can't wait to get in front of everyone and show them what I can bring."
