I don’t have any installation tips but other threads here refer to expanding foam tapes around the frame.
What I can offer is remedial advice.
I had a full thermal survey at the same time as my blower door test and it was clear that while the house was pressurised there was a gale blowing round my frames and in a few cases around casements.
I discovered that installer’s window trims are fitted to hide the appalling quality of the installation. All that I removed had room for improvement and some had a clear view of the garden.
I removed all trims and cut back the plaster as far as was practical. Generally the plaster was damaged, possibly by removing the old windows. I then foamed the gaps, trimmed back the foam to level with the frame and applied Blowerproof from frame all the way to the remaining plaster, thus sealing any air routes through the foam, bricks and mortar. I then made good with wet plaster (a very amateur job) and painted white. Then as rooms are being decorated I am insulating the reveals. I could have insulated at the same time but I was in a rush to complete the job before autumn storms and didn’t have a budget for it.