George is right in that it is a fair amount of work. WikiTree will not simply import the file and ad it to the tree.
When you import the file, WikiTree will attempt to find "reasonable" matches between the data in your file and the data in WikiTree and then present you with the ability to compare those suggested matches and decide whether to accept the match and update the information in WikiTree or reject the match. You are always in control.
There will probably be many profiles in your GED file that do not match anything in WikiTree. For those, you will need to decide to add those profiles to WikiTree or abandon them. Again, everything is under your control.
I get that some will tell you that it might be easier to enter the data by hand but I m not convinced that is true. My aunt's GED file had well over 1000 entries and probably almost that many suggested matches and the format of the GED file does not lend itself to reading the data easily.
If your GED file has only a few entries, it may be easier to hand enter but more than that probably not.
Hope this helps.