Accidently pressed "open with..." and now I dont know how to execute an installer

Hoping the title is self explanatory. Tried to download an installer and execute it but accidently pressed to open it in a text document and now that is the default way it opens. Removed the programs from its "Open With:" options in the file's properties but now every time I try to run it, it asks me to pick a new application to open the file with. Some help would be appreciated.