oldtony
You would need to configure an external repo & download/install from that.
You might have a problem finding a compatible rpm package ie newer vim version & architecture is incompatible with older OS.
For starters see
https://wiki.contribs.org/Category:Yum_Repository& you would search those for a suitable vim pkg, or otherwise google for vim & download & install manually.
As suggested though, continuing to use SME 7 is a BIG RISK.
Best you update SME server eg to SME 9.x & most probably there is a recent compatible vim version easily/readily available.
To upgrade the SME OS you will need to perform a full backup, & then restore that backup to the newly installed SME9 OS.
Note there is no direct upgrade path available due to upstream decisions.